css difference between background: and background-image:

In a background property you can add background-color, repeat, no-repeat and other image attributes, but in the background-image property you are only allowed to add image.

background-image: url("img_tree.png");
background-repeat: no-repeat;
background-position: right top;
background-attachment: fixed;

and in background property you can do in one line all these

background: #ccc url(paper.gif) no-repeat;

By using background, you need to specify other argument to set the background of the page. If you just used background-image, it will only need a single argument.

background: bg-color bg-image position/bg-size bg-repeat bg-origin bg-clip bg-attachment initial|inherit;