Indian Contract Act Section 148 defines bailment. When one person delivers goods to another for some purpose upon a contract that they shall be returned after the purpose is accomplished, it is a bailment. The word 'bailment' is said to have been derived from a French term 'bailor' which means "to deliver".
So now we got the elements of bailment from the definition itself.
There must be two persons.
There must delivery of goods.
There must be a contract or agreement.
There must be an underlying purpose behind the transfer.
The goods must be returned after the purpose is accomplished.
There must be delivery of possession in bailment. It is the sine qua non of bailment.
There is an obligation.
A simple example: In an exam, A gives his pen to B for writing. It is upon an agreement that the pen shall be returned after the exam is over. This constitutes bailment. Here A is the Bailor and B is the Bailee.