These are a Chinese method of first marinating meat, then quickly cooking it so the marinade forms a very thin coating and changes the texture (as far as I can tell, the only difference between the two is that one velvets chicken and slippery-coats pork or beef). This seems to be primarily a western Chinese (Szechuan, Hunan) process, or at least I see it primarily in western Chinese recipes.
The result does not resemble deep-fried food with a crunchy coating.
The meat is marinated in a combination of cornstarch and egg white, with various other ingredients (soy, sherry, etc.) It is then either simmered for a couple of minutes in water, or fried in very hot oil, and drained to be used in the final stir-fried dish.
You can see examples of both in my recipe for Gong Bao Ji Ding and Hot Diced Pork.