The fieldset tag is a very useful tag to make a complex and lengthy form more organized and visually appealing. This technique draws a thin border around a group of form elements so the end user knows they are somehow related. This breaks up a large form into smaller sections that are easy to understand. The legend tag is used to define what text you want to appear in the upper left corner of the selected form elements. For example, if you had a form that collected information about the user, such as their name and address, you could wrap those form elements with a fieldset tag to convey to the user that those form elements are related.
The result on your browser should look like: