Most people don’t bother putting some thought into naming the images they upload to their websites.
That is precisely why you should.
By default, images have got automatically generated names like “img001.jpg” or “1234567.jpg”.
And most web developers will name your template images with names such as “header.jpg” and “footer.jpg”, rather than take the opportunity to insert some keywords such as “search-engine-optimisation-header.jpg” and “search-engine-optimisation-footer.jpg”.
If you take care to name your images with meaningful names, you will be improving the Search Engine Friendliness of your website.
Pimped out bus
For example, search Google Images for “pimped out bus“. My copy of this image is #1 on this planet, just because I named the image “pimped-out-bus.jpg” (this could chance over time).
(And that’s without specifying a “title” or “alt” tag, or writing a caption)
It’s that easy.