A stake is a wooden stick, sharpened on one end and used to mark property lines (or slay a vampire).
In the Middle Ages, people would gamble by placing their bets on wooden posts, or stakes. Eventually the bets themselves became known as stakes. Today, you can use the word as a verb to describe any risky endeavor — for example, "Geoffrey staked his sandwich-making reputation on a six-foot hero with salami and pickles." A stake can also be an investment. If you say that "Bill has a stake in the business," it means he’s a part-owner.