I present here a point-form list of highlights, with links to more detail.
All three mental stats are used
High intelligence lets you learn more spells. High Wisdom gives you more magic points. High Charisma lets you cast your spells more effectively.
rules.spellcasting.detail.paths
Learning spells requires study and dedication. Learning more difficult spells depends on learning simpler spells of a similar nature. This is modeled using pseudoskills called 'spell paths'.
All spellcasters use the same table to determine base spell slots available per day.
Spell selection is spontaneous
Spells may be chosen at the time of casting. There are still benefits to preparing spells ahead of time, but you are not required to do so.