Exactly.
Specifically, the ALT attribute for an image is actually used as the
placeholder text for an image when not loaded. It is also what a screen
reader uses to tell the visually impaired what the image is. IE also will
generate the tooltip which you are seeking.
The TITLE attribute; on the other hand, is use for the tooltip in the other
browsers. IE will also display as the tooltip rather than the ALT
information. The TITLE attribute can also be used for most other tags (<p>
<span> <div> etc) with the same results