Dominaria United Jumpstart Boosters come in ten different themes, and each includes a card describing its theme. Plus you will find both a rare and a rare or mythic rare card:

One random Dominaria United rare or mythic rare in the booster's theme color, and
One rare card designed for these Jumpstart Boosters.
Each Jumpstart Booster also contains:

Several cards from the Dominaria United set
Five non-foil basic lands
Two traditional foil basic lands
One non-foil full art stained-glass basic land