Option symbol is a short combination of letters and numbers that is used to identify a specific stock option. It is like a nickname for the option.
For example, if you own shares of Apple Inc., which is listed as AAPL on the stock market, then the option symbol for an option you want to buy in Apple Inc. might be AAPL110717C120. The first part of the symbol – AAPL – is the same as the stock market listing of Apple Inc. The second part – 110717 – is the date of expiration, which tells you when the option will expire. The last part – C120 – is the strike price, which is the price of the stock when you buy the option.