Practice - Typing Practice tells you your current ability level in all the skills and spells available.
Practice <skill/spell name> - Typing practice <skill/spell name here> allows you to practices that particular skill or spell.
Ex: Practice fireball, practice backstab, practice sword
Your learning percentage varies from 0% (unlearned) to a maximum 75%, any more improvement in the skill is done by using the skill. You must be at a guild master to practice.
Also remember that the higher your memory and reasoning, the more you will learn at each practice session. The total number of bonuses from all the stats on the right column of your score sheet determines the numbers of practices you gain per level.