A quasi contract is a legal concept that is used to create an obligation between parties even if there is no formal contract in place. It is an equitable remedy that aims to prevent unjust enrichment or unfairness.

There are two main types of quasi contracts:

1. Quantum Meruit: This type of quasi contract arises when one party provides goods or services to another party without a formal contract. It allows the party providing the goods or services to claim a reasonable amount for the value of their work.

2. Unjust Enrichment: This type of quasi contract occurs when one party receives a benefit or advantage at the expense of another party without any legal justification. The party who has been unjustly enriched is obligated to reimburse the other party for the value of the benefit received.

In summary, quasi contracts are used in situations where there is no formal contract, but it is necessary to create an obligation to prevent unfairness or unjust enrichment. The two main types are quantum meruit and unjust enrichment.

A quasi contract is not a contract at all because one or the other essentials for the formation of the contract are not present. it is an obligation imposed by law upon a person for benefit of one another even in the absence of a contract.
A quasi contract rests upon the equitable "doctrine of unjust enrichment " which declare that a person shall not be allowed to enrich himself unjustly at the expense of another .Duty is the basis of such contact. quasi contract in India are called as 'certain relation resembling those created by contract '.
A provision regarding Quasi contract are enshrined under section 68-72 of indian contract act these are

1. claim for necessaries supplied to a person incompetent to contract

2. Reimbursement of payment.

3. Obligation for non gratutious act .

4. Responsibility of finder of goods .

5. Liability of a person getting benefit under mistake or coercion.