Special spells are a category of spells that are acquired separately from leveling. Different from Class spells they are located under a tab named Special Spells.
Most of them can be obtained by using Spell-learning scrolls (which are tradable) but there are some that are taught directly to your character upon talking to an NPC.
Special spells can be learned by any class. Some used to have different categories but no longer.
Common spell[]
Formerly it's own category. Can be used in any normal fight.
Summoning[]
Special summoning spells.
Capturing[]
Required for capturing.
Fight specific[]
Required for specific monster types.
Weapon[]
While not truly a spell, your equipped weapon is listed on the Special Spells tab.