Typically a lottery runs in one of two ways: with pre-decided winning tickets, or a number that's drawn after the tickets are distributed to decide which ticket (if any) is the winner. In this way, the odds of winning are mostly independent of the number of tickets sold. The prize is usually money.

A raffle works by selling tickets, and then picking exactly one of those tickets to be the winner, making the odds directly dependent on the number of tickets sold. The prize is usually a physical object, and not money (though there are exceptions, e.g., a 50/50 raffle).