Cantrips are infinite use spells that do not normally take standard attunement slots, but rather, specialized cantrip attunement slots. They are usually not damaging spells, and have a range of utilities and abilities, from creating lights or small flames to silencing the sound of your footsteps.
On a Half Caster class, or a Full Caster class, you start with 1 Cantrip attunement slot at level 1. Multiclassing into another class does not grant the starting Cantrip Attunement slots again.
Full Caster classes receive a feature called Cantrip Efficacy at level 3, 11, and 19, which grants an additional cantrip attunement slot.
Cantrips can be attuned to standard attunement slots if you wish.
Below is a list of Cantrips.