Protective Put

You really like the prospects of a new tech company called Wild Data Inc. You buy their shares at $100 a share. Then...you start to get worried. The firm's CEO keeps talking about the healing power of crystals in interviews, and mentioning how they used to be Fredrick William III of Prussia in a former life. You still think the shares will rise in the future, but you want a hedge against the firm's flakey CEO. You decide to buy a protective put.

A put is an option that pays off if the value of an underlying asset goes down. Essentially, it represents a short on the asset.
In your case, you hope you won't need to use it. You hope shares of Wild Data go up. But you buy the put in case they drop.

If the stock goes up (like you think it should), no big deal. You are out the price of the option, but that's it. Small price to pay for piece of mind. If the stock goes down, you're protected. You'll lose money on the lowered share price, but you'll make money from the put. Hopefully enough to offset your losses.