URL is the acronym for Universal Resource Locator .... basically the precise Internet address for any thing.

An image does not need to be included in a web page to have an address. The image below is called "animal2.gif"

To find out the URL for any image, place your mouse over the image and right-click once. A menu will pop-up. At the bottom of that menu is the word Properties. Click the word Properties.

Another pop-up appears and provides information about the image. One of the bits of information it provides is the image URL

It tells you that the URL is http://www.halfadot.com/freehelp/animal2.gif

Which means that it is on the www.halfadot.com web site, in a folder called freehelp, and the image name is animal2.gif