Options are a specific type of financial instrument. It is a contract between two parties.
Buying an option gives you the right to buy or sell an asset at a set future time at a specific price. A key point with respect to owning an option is that while you have the right to exercise the option you are not required to exercise it if it is not profitable to do so at that future time.
Selling an option obligates you to buy or sell an asset at a set future time at a specific price.