All option contracts have an expiration date. There are two main types of expiration cycles, monthly and weekly. These are called aptly the ‘Monthly’s’ and the ‘Weekly’s’
Monthly’s expire on the 3rd Friday of every month. Weekly’s expire every Friday.
The expiration date is the date at which options are exercised or expire worthless.
Monthly options are more popular and therefore have a more liquid market – Liquidity matters because you want to have markets where you can open and close your positions with a small spread in the bids. Liquid markets are more efficient.