Open your ASP.NET Project,
You'll have two mode,
1.HTML
2.Design

a.Click the HTML,
You'll see HTML and Javascript code.You can code the client side codes there.Its executed on the Client browser.

b.Now come back to Design View and double click design window,Now you be in Code behind(Webform1.aspx.vb),this is server side code.

Now execute your project,Hit F5 and a Internet explorer will be loaded,right click on the Internet Explorer and choose VIEW SOURCE.

You can see how similar your HTML code in you notepad looks when you compare it with HTML code in step a.

I thought I'll give you a practical explanation which will help you understand more.

Hope it helps