While most people use magic through talents, one percent of the population less limited form of magic, the ability to use to control their power. Spells are based around structures and frameworks and allow greater flexibility of effect in exchange for the raw power or precise effect that comes from a talent.
How mages learn spells is dependent on their training and how they manifest. This means some learn through rituals, others through prayers or even raw belief, while others need to work out the ideas using their bodies until they can find the right way to hold themselves to change the world.
Despite their flexibility, mages are typically limited in some manner. A fire mage is one that may be also to cast any fire spell, they may have difficulty or find that they cannot create water, or folding magic. These limitations usually align with the they use as a mental model, so devotees of the Crystal Sphere Techniques would find themselves limited to specific elemental or reactional powers.