is one of the most important and useful
client side state management
It can store the page value at the time of post back
(Sending and Receiving information from Server) of your page.
pages provide the
property as a built-in structure for automatically storing values between multiple requests for the same page.
data is encrypted
and cannot be viewed with software like
FireBugUnderstanding ASP.NET View State
Here you can get detailed description with how you can interpret (and protect) the data stored in View State
Also refer:An Introduction to View State