In 5E, every caster has a unique mechanical quirk. Wizards know spells, prepare spells and have spell slots, and they have the most. Clerics know every spell but prepare a limited number. Warlocks have the fewest spells and slots, but always cast at max level and get slots back on short rest, and can trade known spells on level up. Sorcerers get metamagic. Bard is a support caster who is also a rogue. Ranger is a support caster who is also a fighter. Druid is a support caster who is also a monster. And monk gets psionic spells that aren’t spells and don’t use spell slots.