Domain — Target player draws a card for each basic land type among lands they control.
Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.
The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don’t contribute to domain abilities.
You draw one card per basic land type, not for each basic land. This makes it a maximum of 5 cards.