2. Implied contract:
Where both the offer and acceptance constituting an agreement enforceable at law are made otherwise than in words i.e., by acts and conduct of the parties, it is an implied contract.
Thus, where A, a coolie in uniform takes up the luggage of B to be carried out of the Railway station without being asked by B, and B allows him to do so, then the law implies that B agrees to pay for the services of A, and there is an implied contract.
Similarly, where M, a professional shoe shiner starts polishing the shoes of N without being requested to do so, and N allows M to polish his shoes knowing that M expects to be paid for the service, there comes into existence an implied contract and N is under obligation to pay to M.
3. Constructive or quasi contract:
Such a contract does not arise by virtue of any agreement, express or implied between the parties but the law infers or recognises a contract under certain special circumstances.
For example, obligation of finder of lost goods to return them to the true owner cannot be said to arise out of a contract even in its remotest sense, as there is neither offer and acceptance nor consent, but it is quasi contract as per Section 71.