h1 h2 etc are heading tags in html and are used to determine the most important content.
Default css in browsers will make them appear larger than other type because generally you would want them to be but you can style them however you want.
On your site Levi, I wouldn't have your logo make it a real image on the page. You should then use the alt tag to describe.
Every image should have an alt tag this is used by screen readers for the visually impaired and as replacement text if someone has images disabled and obviously that makes this text also readable by google.
Basically if its an image containing text your alt tag should say exactly that text, if its an image you can describe it alt="picture of a house"
so in your case you could have <img src="images/logo.png" alt="Image Resolutions" />
Then if you wanted to put a h1 tag around it to say this is the most important content <h1><img src="images/logo.png" alt="Image Resolutions" /></h1>
your next line might be the next most important
<h2>Image Resolutions has been providing a multi disciplined design service since 2005.</h2>
using h1 tags will put margin onto your images so you might want to remove that with css
h1 img, h2 img, h3 img {margin:0; padding:0;}
hope that helps