A call option gives the buyer the right to buy the underlying asset a predetermined price (strike price) or receive money if the asset's price is above the strike price. The seller must sell the asset or pay money.

A put option gives the buyer the right to sell the asset at a predetermined price (strike price) or receive money if the price is below the strike price. The seller must buy the asset or pay money.

Equity-style options involve a one-time payment of the premium when the option is purchased, in which case the position is not market-to-market until the option is exercised and no variation margin is required.

The buyer of a futures-style option does not pay the premium to the seller. Payment of the premium is "spread over time" through daily transfers of variation margin until the contract expires, with the initial margin locked in both the seller and the buyer of the option.

Read more about options here