Buying a "call" is buying the right to buy 100 of something at the strike price specified (100 shares of COG at $30, in this case). The amount you pay, the premium, contains a variety of variables which you'd need to understand- "the greeks."

The risk is, if the trade is "bad," and COG dips significantly, you lose out. If you don't (by holding too long) or can't (due to a liqudity issue) sell the call before expiry, you lose the money you paid, the "premium," unless you execute it, which you can't. Meaning, you HAVE to sell the call to make money or get any shred of your money back.

I'm not trying to get banned from this sub, and advising you to buy options would be terrible. Don't buy options until you know what they are.