Ya Anju the main difference is....

Session state and view state are used to keep on certain data.

View State:

- View state is maintained in page level only.
- View state of one page is not visible in another page.
- View state information stored in client only.
- View state persist the values of particular page in the client (browser) when post back operation done.
- View state used to persist page-instance-specific data.

Session State:
- Session state is maintained in session level.
- Session state value is available in all pages within a user session.
- Session state information stored in server.
- Session state persist the data of particular user in the server. This data available till user close the browser or session time completes.
- Session state used to persist the user-specific data on the server side.

ViewState:-1.ViewState of one page is not visible to another page.2.ViewState is maintained at page level.3.ViewState variables store the value for a single page.

SessionState:-1.SessionState accessible to all page.2.SessionState on the other hand maintained at the session levele.3.SessionState store the value for the full project.