How to use the font-awesome library with ajax : I might be asking a dumb question, but I am a newbie in javascript and its libs.

I came across the same problem as [this post][1], and in the accepted answer, there was this line 

    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">

However, after adding this line I have a navbar icon even though I did not include a img in my html. I also cannot manipulate the position of this icon built with this stylesheet. Can anyone explain what it does in this context? (referring to the [post][1]) I noticed that without this line of code the CSS and Javascript cannot be applied to a simple 
`<img class="search" src="icon.png" width="30" height="30">` 

And how is it possible for me adjust the location of the icon with this line of code? 


  [1]: https://stackoverflow.com/questions/46803710/how-to-make-a-drop-down-menu-from-an-icon-in-a-navbar