What are Quasi Ciontracts?

Section 68 to 72 of the Indian Contract Act deals with Quasi Contracts. Inceratin cases  although there is no will or volition is expressed for creating contractual obligation and no regular acceptance hasbeen made by the parties there are transactions which resemble to contracts. For eg A supplies B a lunatic with necessaries suitable to his condition in life, A is entitled to be reimbursed from B's property.