Learn how Pokémon breeding works in different games, when two Pokémon are compatible, and which items are useful for getting better IVs, Natures, and baby Pokémon.
Basically, you create an Egg by using two compatible Pokémon together. In older games, you do that through the Day Care or Nursery, and in Scarlet/Violet through a picnic.
Usually, Pokémon need to be in the same Egg Group to produce an Egg.
Many Pokémon can breed with Ditto, including genderless species.
The baby is usually the species of the mother, or of the non-Ditto parent.
Legendary Pokémon and species in the No Eggs Discovered group usually cannot breed.