The difference between sweepstakes and lottery primarily lies in the requirement of purchase and the method of entry. Sweepstakes are promotional contests where participants enter for free, often by submitting their information, with winners selected at random. In contrast, a lottery typically requires participants to purchase a ticket for a chance to win cash or prizes, with winning numbers drawn at random. Understanding the difference between sweepstakes and lottery is essential for participants to ensure compliance with legal regulations and to choose the right type of contest to enter.