>>56681074cantrips are free spells that you can cast whenever
level 1-9 spells are slotted spells, you can upcast spells if you've spent lower level slots which sometimes will add more damage at higher levels (like another 1d8 or whatever), but it consumes the higher level spell slot, so you could cast a lvl 1 spell at lvl 3 and it would consume a level 3 spell slot
some spells are ritual cast, which means they take 10 minutes of in game time for the ritual to be cast and dont consume a spell slot when theyre used, but the 10 minute thing doesnt apply in bg3, its just a free spell which isnt combat oriented typically
other "spells" and effects can restore on short rest, like wild shape, and then theres stuff like arcane recovery on wizards which can refresh spell slots
