In general, there are two things that are required in order for a contract to be considered legally binding: consideration and consent. Consideration refers to the requirement that each party in a contract must be benefited in some way from the agreement. Consent is the requirement that both parties are in the agreement freely.
Most contracts have a clause under which the agreement may be voided. A contract that has been breached by another party can sometimes be terminated by the group that did not breach the contract. The specific language of the contract will provide any exit clauses and if you are seeking to get out of a contract, a contract law attorney should be consulted.
The consequences of breaching a contract vary depending on the nature of the contract. A loan agreement that is breached may result in the forfeiture of the property the loan was used to purchase. Breach of a business agreement may result in civil or financial penalties.
An expressed contract is explicitly stated and codified in some way, either physically or digitally. Expressed contracts are more enforceable and easy to dispute in court. Implied contracts are not explicitly stated but instead are assumed on the part of the parties with no formal contract agreement being present.
In order to ensure a contract is enforceable, the language must be clear and enumerate all circumstances foreseeable by the parties. All parties must enter into the contract willingly, and they must also receive some type of compensation for signing on to the agreement.