Hangman comes from the vicious time in late-19th century Britain called the Victorian era. (Ok, it's more known for its obsessive decorum and rather uptight mores, but maybe a game where the loser is represented by a man hanging from a gallows was a way to let loose.) It's easy enough: One player thinks of a word (or phrase) and writes blanks for every letter below an ominous-looking gallows with a rope. The other player guesses letters until the word or phrase can be sussed out. The only wrinkle is that for each wrong guess, another body part is added to the swinging rope. (Six body parts are standard: head, torso, two arms and two legs.) You have to fill in the blanks before the man is drawn in completely or you lose (not to mention confronted with your own precarious mortality).
If you're looking for an extremely hard word or you just can't think of anything, there are Web sites (complete with algorithms) that will give you suggestions for the most challenging Hangman words. Interestingly, short words seem to dominate, along with words that have repeated letters. Thus, "jazz" comes out as a top head-scratcher.