A cad is someone who can be quite charming, intelligent, capable of engaging in stimulating conversation, ultimately presenting himself as a gentlemen. A cad, however, is not a gentleman because he systematically cons lovely ladies into falling in love with him and then openly cheats on them. He is completely selfish with only feigned regard for women's feelings. Somewhat like a playboy but instead of being open about his philanderings, a cad usually pretends to care about a woman before coitus, thereby confusing the woman when he drops her like a hot potato. He is dishonest with most people around him (often even himself). Cads also frequently have addiction issues.
Dude 1: Is James Bond a cad?
Dude 2: Nah, at least the Bond Girls don't expect him to stick around and he doesn't pretend to make them feel special.