Cartwheel is the name of Diddy Kong's frontal attack and it is, as the name would imply a cartwheel.
The move is first utilized in Donkey Kong Country and Donkey Kong Land. The attack lets Diddy take an enemy by cartwheeling into them, if used on a row of enemies the attack may take the entire row out. A cartwheel is ineffective against bulky enemies (such as Krushas), spiked enemies such as Zingers or bosses. Also if Diddy cartwheels off a ledge he will be able to jump in midair, thus extending his jumping radius.
Diddy's cartwheel attack returns in Donkey Kong Country 2: Diddy's Kong Quest and Donkey Kong Land 2. The cartwheel remains relatively unchanged in these games.
Diddy can also use his cartwheel in Donkey Kong 64, where it is one of his basic moves.