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. (Read more)

      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. (Read more)