I am pretty new in Twitter BootStrap and I have the following doubt.
I have clear how the BootStrap grid layout works so if I have something like this:
<div class="row">
<div class="col-md-4">
<div class="col-md-4">
<div class="col-md-4">
</div>
simply means that I have a row divided into 3 columns of the 4 dimension (because the BootStrap grid layout is based on 12 columns)
My doubt is related to the md definition of these columns.
I know that I can use also something like <div class="col-xs-4">
What exatly is the difference between the col-md-4 class and the col-xs-4 class?