Not quite, you're mixing things up. The "alt" attribute specifies the text that's displayed if the image can't be loaded - it's supposed to be an alternate representation of the information in the picture, so if the picture is missing, or you have a text-only browser, or a blind user using text-to-speech, or any other reason why you need a text representation of the picture, it's there. Meanwhile the "title" attribute (not just on images, on any HTML element) stores "extra" information, which is displayed by most browsers in a mouseover tooltip.
Referring to the mouseover tooltips as "alt-text" is a misnomer that dates back to the fact that ye olde versions of IE would display alt text in a tooltip (and didn't recognise the "title" attribute), so website builders would break with the intended usage of the alt attribute and put tooltip-appropriate text in there. IE has since corrected its ways, but the name has stuck.
While no one overhear you quickly tell me not cow cow.
but how about watch phone?