Contracts are verbal or written agreements that parties enter consensually, exchanging consideration. Use this tag when the question is about contracts, or one or more elements of a contract.
A contract is the creation of legal obligations between parties, who exchange consideration. Those who enter into contracts must have the capacity to do so, and the intention to be legally bound.
As an example, everyday purchases are verbal contracts that people enter into: a buyer agrees with a seller that they will purchase an item for a certain price, or in exchange for an item or service. Such a contract requires some form of acceptance by the offeree, which may be the act of ordering a meal, or clicking an online order submission. A signature is not universally required, but is taken as strong proof of acceptance.
While contracts can be verbal or written, in some regulated markets, for example, real estate, statutes may exist that impose further obligations on the parties to conduct the transaction with a written contract.
If the question is about the law applicable to contracts, consider using contract-law either alone or in addition to this tag.