Cantrips

A cantrip is a special type of spell that's weaker than other spells but can be used with greater freedom and flexibility. The title of a cantrip's stat block says “Cantrip” instead of “Spell.” Casting a cantrip doesn't use up your spell slots; you can cast a cantrip at will, any number of times per day. If you're a prepared caster, you can prepare a specific number of cantrips each day. You can't prepare a cantrip in a spell slot.
A cantrip is always automatically heightened to half your level, rounded up. For a typical spellcaster, this means its level is equal to the highest level of spell slot you have.

Seplls

Characters of spellcasting classes can cast a certain number of spells each day; the spells you can cast in a day are referred to as spell slots. At 1st level, a character has only a small number of 1st-level spell slots per day, but as you advance in level, you gain more spell slots and new slots for higher-level spells. A spell’s level indicates its overall power, from 1 to 10.