Tag in AJAX

Question

Hi

I am working in ajax and face a probleam in <span>tag. define what is <span>tag .can i use in place of <DIV>Tag?
       
<form>
<input type = "button" value = "Display Message"
onclick = "getData('http://localhost/ch01/data.txt',
'targetDiv')">
</form>
<div id="targetDiv">
<p>The fetched data will go here.</p>
</div>
</body>