The world of Albion has six Schools of Magic. They each represent not only a set of spells, but a way of looking at the world - a method of study and practice. As a result, they are mutually incompatible. One who has a natural aptitude for Theurgy will simply never be able to learn Conjuration; their brain does not work in the right way.
You may choose to start the game as a Magician, or not. However, since the six Schools are widely known about, it is worth at least reading the brief summaries of each below to get an idea of your character's IC knowledge.
It should be stressed that in the view of most residents of the world of Albion, there is no practical difference between magic and science. The words are frequently used interchangeably, and a mathematician or astronomer is as likely to be called a “Magician” as a Conjurer is a “Scientist”. Both practices focus on exploring and examining the nature of the universe, and on manipulating it whenever possible.
Thus, Invention, for example, is not less 'magical' than the other Schools because it involves mechanical components which work on physical principles also present in our real world; nor are the parts of Witchcraft which involve using mandrake to curse any more magical than those which involve using willow-bark to kill pain. Magic represents a way of looking at the world rather than just a tool – Alchemists’ studies make them more inclined to see things in terms of their physical composition, Theurgists in terms of their philosophical or divine purpose, Inventors by how they are put together and so on.
For more details, see Religion and Magic.
Spells can be cast slightly different in each school of magic. The most common method however is a set of preparations, notably obtaining the necessary Token, followed by a specific ritual to cast the spell.
This is usually described, including intent and purpose, in one's turnsheet.
Some spells from the school of Conjuration can be cast long after they have been 'prepared' in a ritual - which includes the possibility of casting them in Court.
Summoning spells from the schools of Theurgy and Sorcery usually need a relevant circle to be 'cast' before they are performed.
Any Magical project or ritual requires, in addition to a number of mundane materials, items or ingredients you are assumed to be able to obtain trivially, one or more Tokens which are key to the project and may be difficult to obtain. Examples might be a particular type of wood for an Invention, powdered unicorn horn for an Alchemical preparation, etc. Unless otherwise stated, these Tokens are not reusable - the Spell either destroys the item or makes it otherwise unsuitable for future use.
Generally speaking, unless you can find a particularly good source for acquiring Tokens, you will be expected to spend AP on obtaining them. However, on several occasions, PCs' abilities and possessions will cross over - a difficult Token for a Theurgist to obtain might be trivial for an Alchemist, or a Priest. You may also be able to spend AP on discovering a permanent source for Tokens, or obtain several batches of a substance or item at one blow, with a clever plan.
It is impossible ever to know more than one of the Schools of Magic, and many go their entire lives without even going so far as to dabble in one.
Main article: Conjuration
Conjuration is a factotum's magical school; showy, practical and varied. A broad school taking on ideas and spells from all the schools, giving the conjurer a wide variety of different spells to work with. Most importantly a conjurer can create their own spells! These can be applied to almost any situation but will always be less powerful than the most advanced in other schools.
Main article: Witchcraft
Witchcraft has long been considered the preserve of the commoner woman who speaks with spirits and delivers babies. Witchcraft is very user-friendly magic with a host of spells working with herbs and interacting with Familiar Spirits.
Main article: Theurgy
Theurgy is practiced by many clergymen and Rabbis, but not unknown in the laity. It focuses on summoning, entreating and interacting with Angels.
Main article: Sorcery
Sorcery has an evil reputation in many quarters. It is the School whose purpose is to summon, bind and speak to Demons. Though practiced by some priests, and not heretical per se, it has that particular frisson of danger which leads many young, bored nobles to think it will make them more attractive to the opposite sex.
Main article: Alchemy
Alchemists work with the four elements - they manipulate them and work them to produce objects with magical affinity or ability. Alchemy concerns itself with brewing potions, changing objects and imbuing items with special effects.
Main article: Invention
Invention is the magic of the gentleman scholar. It allows devices to be created which interact with other magics in various ways. From Alchemical power sources and Familiar Spirit chauffeurs to Inscribers to keep a Theurgist's ritual circle intact, the Inventor is the friend of all other magicians. Leonardo DaVinci is maybe the most famous Inventor of all time, creator of the first Flying Machine and many other famous Inventions.
Casting spells and doing research does not have to be limited to one magician only and some co-operation is encouraged. There are however, as always, some dangers involved when trying to perform something that has not been done before, or only rarely.
The most obvious and straight-forward co-operation is between the school of Conjuration and the others, since conjurers are adept at finding or even producing various tokens. Many make a living out of supplying various medium-level tokens to the elite practitioners of the country.
Inventors also need the help of other magical practitioners to acquire the tokens needed for their creations - familiar spirits, alchemical preparations, rare items and possible even angels or demons. Witches, Alchemists, Conjurers, Theurgists and Sorcerers are all useful to the Inventor. And in return, they can create devices to assist the other schools in their magics.
More complicated interaction is however certainly possible. As with all experimental magic, the further one steps from the beaten path, the more risks one is likely to encounter.
Co-operation within schools is the obvious way to speed up any spell, or to increase its effectivenes and decrease the chances of things going wrong. Co-operation can potentially however be dangerous if the mages happen to be at cross-purpose (and indeed the question of deliberate sabotage is never too far away).
Two Magicians working together in one School may be able to advance faster, or further along their chosen path, and indeed many of the greatest and most powerful spells on record have been discovered in this way. Generally, two Magicians who know the same spell can choose to split the AP cost and share the work of casting the spell; or, alternatively, can attempt to cast two separate spells in an attempt to bring about an effect greater than the sum of their parts. More complex uses may be possible - please do talk to the GMs if you have an idea.
Consequences of things going wrong in a basic spell within one school will be the same as if one magician was performing the spell (though obviously with a chance of reduced effect).
Consequences behind inter-school spells and casting are likely to be unpredictable, taking aspects of the schools involved. There will always be specific reasons and clear mechanics behind this, but not all of them will be apparent or revealed to the players.
Different schools adopt a different method of advancing within the schools and learning new spells. Consult the individual pages for detailed explanations. The base cost of any learning or creating of spells is 4AP, though this can be modified depending on school specifics.
Experimentation is a life-force in magic and its study and is (cautiously) encouraged by established authorities. There is always something new that can be discovered by doing things differently, or trying things that haven't been done before. This is obviously more dangerous if you're trying say, to summon a demon into a circle made out of people's memories than the required gold dust, but it may work (or your head may be removed, kept alive, and made to relive nightmares in the demon's living-room).
Experimenting takes on different guises in the different schools, though it is usually to do with modifying spells, or researching into ways to make them work differently.
It is, of course, also possible to learn about magic rather than learning magic. For a quantity of AP - usually half or less the cost of learning the actual spell - a PC can research around a spell if they have its name, learning the details of its Ritual, Tokens and possibly even ways to ensure its safe casting.