Hyperlinked, tool-tipped, image:
<a href=for_more_info.php title="red striped jumper">
<img src=images/red_jumper.jpg>
Buy this dashing garment
</a>
You can reference multiple images (above) in a single <html> file.
> Will I have to create a new file for EVERY image I use??
Eh? Yes, each image will be its own file (eg images/red_jumper.jpg).
(Suggested, but not required: Put all the images in a separate directory, as I did with "images/".)
If you are doing both thumbnails and full-sized images, recommend you build both images, with slightly different filenames (such as prepending 't' for the thumbnails).
Sure, it is possible to use height= and width= in <img> to shrink the full image to thumbnail size, but it costly for the user -- his browser has to download the full image, then shrink it.