Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Job Offer - Explain Stock Options [US]
An option is a financial instrument instrument that gives you the right, but not the obligation, to do some transaction in the future at a given price. An employee stock option is a kind of "call option" -- it gives you the right, but not the obligation, to buy the stock at a certain price (the "exercise price", usually set as the price of the stock when the option was granted). The idea is that you would "exercise" the option (buy the stock at the given price as provided by the option), if the value of the stock is higher than the exercise price, and not if it is lower. The option is gifted to you. But that does not mean you get any stock. If and when you choose to exercise the option, you would buy the stock with your own money. At what time you can exercise the option (and how many shares you can exercise at a given time) will be specified in the agreement. Usually, you can only exercise a particular share after it has "vested" (according to some vesting schedule), and you lose the ability to exercise after you no longer work for the company (plus perhaps a grace period), or after the option expires.