A forward contract is a customized agreement between two parties to buy or sell an asset at a predetermined future date and price, with no upfront payment required. It is used primarily for hedging and has counterparty risk.
A futures contract is a standardized agreement traded on a futures exchange to buy or sell an underlying asset at a predetermined future date and price, with an initial margin payment required. It is used more for speculation and has low counterparty risk due to clearing house guarantees.
The key differences are that forward contracts are customized over-the-counter agreements while futures contracts are standardized exchange-traded agreements, with futures requiring an initial margin and having a clearing house to reduce counterparty risk.