A pledge arises by virtue of a contract. A pledge also may arise on the basis of a statute upon the occurrence of the circumstances indicated in it if the statute provides what property is recognized as being in pledge and for securing the performance of what obligation.
A pledge may take the form of:

1. a deposit;
2. a pledge of goods in a pawnshop;
3. a pledge of rights;
4. a pledge of monetary assets;
5. a firm pledge;
6. a pledge of goods in commerce;
7. a mortgage.

Source: Iravaban.net