When something is agreed to by two or more competent persons voluntarily with a view to bind each other and create mutual  rights and duties ,such understanding not tainted with fraud, misrepresentation, coercion and occurred with identical object, purpose,subject and object for mutual lawful promises is a contract.
If the relationship so created is insulated in such a way as to prevent or restrict the free flow of consent, understanding,aims and object the relationship may fall short of contract and may take a shape of other legal terms that may give rise to other civil or criminal consequences.
A judge has to deal with all such types of contracts,quasi contracts, neo-contracts, anticipated contracts,, disputed contracts,repudiated contracts, tainted contracts, unfair contracts,legal contracts, illegal contracts,void contracts (contract non-est),voidable contracts, impossible contracts, private contract, public contract ( tort),express contract,implied contract.