Let's say I sell you an option to buy (from me) a share of TWTR at $100 at any time through the end of January. I have just sold you a call option. If I alread

Let's say I sell you an option to buy (from me) a share of TWTR at $100 at any time through the end of January. I have just sold you a call option. If I already own a share of TWTR that is not tied up in another contract, the call is considered covered (meaning I would not have to go out and find a share to buy if you exercised the option). More: https://en.wikipedia.org/wiki/Covered_call https://en.wikipedia.org/wiki/Covered_call