A contract is an agreement between parties, creating mutual obligations that are enforceable by law. The basic elements required for the agreement to be a legally enforceable contract are: mutual assent, expressed by a valid offer and acceptance; adequate consideration; capacity; and legality.
As soon as you gain access to contracts from corporations, each corporation will offer you to complete only one contract, which is a kind of test of your suitability. After its completion, the corporation will issue your contracts for which you will receive a reward and increase your reputation with this corporation.