Whomp 'Em is an action platformer, akin to many games at the time. It is notable for being one of the few video games to feature a Native American as the protagonist. After completing the first stage, the player can play the other six in any order. Each of the stages revolve around elements, such as fire and water. After each stage, the player gains a new weapon, much like in the original Mega Man series, which was extremely popular at the time.
Both Whomp 'Em and its prequel (which was an adaptation of Wonder Boy in Monster Land), are based on the Journey to the West novel.
The title, "Whomp 'Em" is a pun, based on wampum, white beads used by Native American tribes primarily for trading.
Source: Wikipedia, Whomp 'Em , available under the CC-BY-SA License.