Spell memorization

Bards, Favored Souls, and Sorcerers have to memorize what spells they can use upon character creation, and while levelling up. Unfortunately, unlike D&D, neither currently have the option to swap out older spells for newer spells at level up. However, every three days, you can talk to your class' trainer to swap one of your spells for another one of the same level.

DDO also sometimes uses the term memorize when it means inscribe if you're looking for info on Wizards.

See also Spell preparation, as it often gets confused with.