Options are a contract between a buyer (holder) and a seller (writers).
Call options: the holder has the right to buy; the seller has the obligation to sell at the predetermined price and quantity.
Put options: the holder has the right to sell; the writer has the obligation to buy at the predetermined price and quantity.
The holder (buyer) always pays the premium to the seller, which sets the maximum price. The option premium is what the buyer must pay to get the right to buy/sell the underlying assets. Therefore, the most that the option buyer can lose is the premium paid.
Writers (sellers) must always fulfill the obligation.
