Fry refers to a life (growth) stage of fishes that are recently hatched.  This is generally after the yolk sac has been absorbed and almost or entirely disappeared.  At this point, the swim bladder is typically functional and fish can actively feed for themselves.  Depending on the species, this stage can last a few months or more until scales develop.  

Coho Salmon fry (photo credit: City of Surrey).

Fry can be thought of as the “infant” stage for fishes.  Because of their small size at this stage (often only a few centimeters), fry are vulnerable to predation in this stage and need shallow, protected habitat to feed and grow. (fishionary.fisheries.org/fry/)