What is the difference between <p>, <div> and <span> in HTML&XHTML?

Question

What is the difference between <p>, <div> and <span>?

Can they be used interchangeably?

Because I am facing problem that, for <span> margin not working but for the <div> and <p> it's working..

Answer 1

p and div elements are block level elements where span is an inline element and hence margin on span wont work. Alternatively you can make your span a block level element by using CSS display: block; or for span I would prefer display: inline-block;

Apart from that, these elements have specific semantic meaning, div is better referred for a block of content having different nested elements, p which is used for paragraphs, and span is nothing but an empty element, hence keeping SEO in mind, you need to use right tag for right thing, so for example wrapping the text inside div element will be less semantic than wrapping it inside a p

Answer 2

A <p> should contain paragraghs of text, a <div> is to layout your page using divisions and a <span> allows markup to be styled slightly different, for example within a <p>

This is how they should be used semantically, the styling of them however using CSS is up to you.