Helps about Ajax

I'm new to the AJAX concept.

Any one help me to how use the AJAX in C#.Net.

Some of the helps which describes using the Ajax.dll (third party) and some other used in Ajax Extension. How to use the basic ajax in C#.net.

Give me the best examples to understand easily.

Advance Thanks,

Tutorials, samples, and so on.
http://www.asp.net/ajax/documentation/live/