There are all kinds of sweepstakes and lottery scams, and most originate in foreign countries.
There is one important thing to keep in mind:
FOREIGN LOTTERIES ARE ILLEGAL IN THE UNITED STATES
These scams will tell you that you’ve won a whole lot of money, and in order to claim it you have to send in a smaller amount of money. They will also tell you to keep it confidential until they’re ready to announce your big winnings.
These kinds of scams often use celebrities or other famous names to make their offer seem more genuine. If you aren’t sure, don’t click on the link but instead go directly to the homepage of the company mentioned. If they are really giving away $1 million, there will be some kind of announcement on their website. But don’t waste too much time looking.