I am fairly new to CSS and have a question that is probably really easy to answer. I am setting up a site using a theme and noticed that there is already styling in the CSS for images. I have been trying to call to the styling, but have not had luck. I guess I was just curious about what I would do to call to this image style so that I could apply it to several images.

I thought <img class="internal"> would work. but I was wrong. The css looks like this:

img.internal { border: 1px solid #DAD5D5; padding: 5px; }
img.internal { border: 1px solid #DAD5D5; padding: 5px; }
img.size-auto, img.size-full, img.size-large, img.size-medium, .attachment img{max-width:100%; height:auto; }
.alignleft, img.alignleft{display:inline;float:left;margin-right:24px;margin-top:4px;}

The styling continues for about 15 more lines. I am not familiar with calls that don't start with a . or #. Again, I am new to CSS so any help with this would be appreciated.