An oranda is a type of goldfish

Goldfish

The goldfish is a freshwater fish in the family Cyprinidae of order Cypriniformes. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish....

 characterized by a prominent raspberry-like hood encasing its head. The hood or headgrowth (also known as wen) encases the whole head except for the eyes and mouth.
Due to the fleshy outgrowth on the upper half of its head and sides of its face, the oranda has become one of the most popular goldfish. It is described as a wen by the aquarists.