An option chain is a comprehensive list that shows you all available option contracts for a given stock. These are sorted by their expiration date, which is the last day you can trade or use the option, and strike price, which is the price at which you can buy (call) or sell (put) the stock.
A call option buyer stands to profit if the underlying asset, say a stock, rises above the strike price before expiry. A put option buyer makes a profit if the price falls below the strike price before the expiration.