EPS stands for Encapsulated PostScript. Vector EPS-files can be opened in Adobe Illustrator, Adobe Photoshop, as well as CorelDraw, GIMP and InkScape.
In vector graphics information is stored as a collection of geometrical shapes. That means that you can open a vector graphics file and render it as large as you want. You can also change geometrical values without distorting the image or loose quality. In order to get a vector graphics you'll need to buy the large, original file. The price is only $19.50.