Equity option

a contract that gives its owner the right, but not the obligation, to either buy (call) or sell (put) 100 shares of a specific (underlying) stock or exchange-traded fund (ETF), at the strike (exercise) price, upon the contract's exercise. Equity options are American-style, and so may be exercised at any time before they expire. Their value is based on the value of the underlying stock or ETF.