what gives the end of .aspx ??

[auriaks]

I think the title is informative... Why we use this ending?

[djr33]

It's the file extension for (X)HTML pages generated by ASP.
It's similar to .asp

It's just like .php, except that it uses the ASP language, not PHP language...

For more info, try a search:
http://en.wikipedia.org/wiki/Aspx