Tài liệu Scripting and (X)HTML

The value of the action attribute is a URL, so you can use absolute or relative
URLs to point to a form handler on your server. Absolute and relative
URLs are covered in more detail in Chapter 6.
Input tags
The tags you use to solicit input from your site visitors make up the bulk of
any form. HTML supports a variety of different input options — from text
fields to radio buttons and from files to images.
Every input control associates some value with a name:
✓ When you create the control, you give it a name.
✓ The control sends back a value based on what the user does in the form.
For example, if you create a text field that collects a user’s first name, you
might name the field firstname. When the user types her first name in the
field and submits the form, the value associated with firstname is whatever
name the user typed in the field