• Offer : 

A person is said to have made a proposal/offer when he signifies to another, his willingness to do or to abstain from doing anything with a view to obtaining the assent of that other to such act or abstinence. In simple words – an offer is a proposal by one party to another to enter into a legally-binding agreement with it.

• Agreement : 

A proposal or offer when accepted becomes an agreement. 

An agreement, is an accepted proposal:

 Agreement = Offer + Acceptance.

• Cross-offer : 

When two parties exchange identical offers in ignorance at the time-of each other’s offer.

• Executory contract :

A contract in which both the parties have to still fulfill their respective promises.

• Pledge : 

The bailment of goods as security for payment of a debt or performance of a promise is called pledge.

• Lien : 

Right of one person to retain possession of some goods belonging to another until some debt or claim of the person in possession is satisfied.

• Bailment : 

It is the delivery of goods by one person to another for some purpose upon a contract, that they shall, when the purpose is accomplished, be returned or otherwise disposed of according to the direction of person delivering them.

• Injunction : 

When the court, by issuing an order, restrains the party in breach of a negative term of a contract from doing what he promised not to do, such order is called as injunction.

• Quantum Meruit : 

A right to sue on a quantum meruit arises where a contract, partly performed by one party, has became discharged by the breach of the contract by the other party, i.e. right is founded on an implied promise by the other party to pay for what has been done.