Explain who Compeyson is and how Pip has met him

In one of his brief stints actually out of jail, Magwitch met a young well-to-do gentleman named Compeyson who "had the head of the devil." Compeyson had his hand in everything illegal: swindling, forgery, and other white collar crime. When Magwitch met him, Compeyson was working with a half-crazed man called Arthur, who saw visions of a woman dressed all in white, with a broken heart, who came to haunt him. On one of these haunts, Arthur gave up his own ghost and died.

Compeyson then recruits Magwitch to do his dirty work and soon gets Magwitch into trouble with the law. Both standing before the judge, Compeyson, being a gentleman, is given a lesser sentence than Magwitch, a career criminal. Magwitch hates the man.