The stock option given to you means that when the specified time comes (such as when the company goes public), you can buy a specified number of shares (that is, hundreds of thousands of shares) at the price specified in the option. Of course, there is an extra charge for buying stocks. Generally speaking, this price will be lower than the market price, and you can sell the stock and earn the difference. Sure, you can keep it. The higher the company's share price, the more it earns.
If the specified price is lower than the listing price (basically impossible), you can also choose not to buy enough shares, so there is no effort and no gain.
The purpose of PS company issuing options is to motivate employees. After all, only if employees work hard, the company's benefits will be better, the stock price will be higher, and then employees can earn more through options.