It means that the prices you see to download an image gives you the right to use that image for a wide range of both commercial and personal purposes. For personal use, you could (for example) make as many prints of the image as you like and give them to your friends for presents. You cannot, however resell the prints or the image file.
That applies to commercial uses as well. As a commercial user, you have the right to make one print of the image. Larger orders will have to be negotiated. You can use it on as many websites as you wish. You can use it for advertising purposes, such as print ads, or billboards.
However, if you wish to place ads in more than one magazine (for example) that will also need to be negotiated. If you wanted to use the images in a television or web broadcast - that's also fine.
The main idea is that it isn't fair to purchase one file and use it multiple times. Again, a description of usage would be necessary and agreed to by both parties.
Contact me to discuss licensing multiple uses of a single file.