The basic difference between them is that a div is block level element and a span is inline level element.
<span> and <div> tags both allow a Web designer to style text and add other formatting attributes to their Web page. They are not interchangeable tags though. <div> tags are block-level elements, whereas <span> tags are not.
Div
<div> tags are block elements that allow you to position elements contained within them
Example
<div style="color:#00FF00">
<p>This is a paragraph.</p>
</div>
Span
<span> tags are NOT block elements
<p>The quick <span style="color:brown;">brown</span> fox jumps over the lazy dog.</p>
