Where should I use the <div> tag?

Answer 1

Div is used inside body tag
Div tag is used as a container for other html elements. it also used for styling with css.

Answer 2

It's a box that can fit other html things inside it
It goes inside the body tag

Example

<div><h1>hello<h1/></div>

You can customise it with CSS
Change its size,color etc🙂

Answer 3

Where you want.You can use division that englob one element or more to separate it from other and to set its own style or position on the page.You can use div inside other inner/outer parent/child.