Legality of object refers to the requirement that the purpose or object of a contract must be lawful for the contract to be enforceable. This means that contracts with illegal objectives or that require illegal actions are generally not enforceable in court.

Consideration, on the other hand, is something of value exchanged between parties in a contract. It could be money, services, goods, promises, etc. Both parties must give something of value for a contract to be valid. It ensures fairness and distinguishes a contract from a gift or a one-sided promise.

In summary, legality of object ensures the contract's purpose is lawful, while consideration ensures there's a fair exchange between parties for the contract to be binding.