How to use form inside other form?

I want to post some of the fields for add product. Here I have to upload the product using jquery. For that I have to use form.

I got some code from one site like this

<div>
<form>
<input type="text" id="ptitle" class="error" name="prd-title">
<input type="text" id="pdescription" class="error" name="prd-desc">
<form  action="" class="imgupld" method="post" enctype="multipart/form-data">
<input type="file"  class="imginput"  name="images"  multiple="multiple">
</form> 
</div>

1. How to use form within form?


2. Is this standard code? Thanks