What!
Question: Plz tell me
Answers: Plz tell me
gangrene is an infection of a wound for example, where the tissues start to die(become necrotic) due to bacterial effects on it. (bacteria eat the tissue, it dies) or when theres no blood reaching it (for example, diabetic gangrene)
a hematoma is a clot under your skin when you are hit but the outer layers are not cut (a bruise)
need more details?
Gangrene is infection or ischemia (that's like a blockage of blood supply). Hematoma is a large collection of blood under the skin, like a large bruise.
Good Luck
EDIT: Ischemia can cause gangrene if left untreated.