What is the difference between a white dwarf and a black hole?

Answer 1

A white dwarf is the final stage after the death of a star roughly the size of our sun. It is composed mostly of nickle and iron metal (the end products of nuclear fusion) and is initially very hot (i.e. "white"). Eventually it will cool off becoming a black dwarf and nearly impossible to detect.

A black hole is the final stage after the death of very massive stars. The mass of the star is so great that the force of gravity completely overwhelms any repulsion of the other three forces and quantum effects that prohibit matter from occupying the same place. The entire star's mass collapses into a single infinitesimally small point and an "event horizon" forms around this point where gravity is so strong that nothing including light can escape out of and anything falling through it will fall into that point with no chance of escape.

Stephen Hawking also hypothesized that the big bang also created many microscopic black holes that due to quantum effects radiate mass and energy faster and faster as they get smaller, until they suddenly explode destroying themselves. (Note: black holes created by the collapse of large dead stars cannot do this)