A contract is anything two parties agree to with some consideration (benefit) exchanged. The law does not distinguish between 'proper' contracts and informal on

A contract is anything two parties agree to with some consideration (benefit) exchanged. The law does not distinguish between 'proper' contracts and informal ones (like a handshake) except a proper one may be quicker to execute. And this is a feature... You wouldn't want to force everyone to undertake the cost of developing highly specialized legal products just to do business.