Edit in JSFiddle

#special_para{
    color:purple;
    font-size:12px;
}
p.center
{
color:red;
text-align:center;
} 
p.justify {color:blue;text-align:justify;}

<p class="center">Learning id and class</p>
<p class="justify">This paragraph is using the class justify. Can you notice the difference? We hope that now the concept of class and id are pretty clear to you.</p>

<div id="special_para">This TEXT is using ID. It can be used by other HTML elements also.</div>