鼠标悬停Ajax + PHP

In my website at the moment my shop just show the icone of the item here is a example:

What I want is to when you pass the mouse over the icone show another image that would be a description of the item.

I made the form already to upload both pictures etc this how my db is looking.

The actual code to get the icone for the items is looking like this

foreach ( $stdItens as $item ) {
                               $itemObjID = $item [ "objectID" ] ;
                               $itemID = $item [ "itemID" ] ;
                               if ( strlen ( $item[ "icon" ] ) === 0 ) {
                                      if ( file_exists ( sprintf ( 'Images/shop/icons/%d.png' , $itemID ) ) ) {
                                             $image = BaseURLConcat ( 'Images/shop/icons/' . $itemID . '.png' ) ;
                                      } else $image = BaseURLConcat ( 'Images/shop/icons/noIcon.png' ) ;
                               } else {
                                      if ( file_exists ( $item [ "icon" ] ) ) {
                                             $image = BaseURLConcat ( $item [ "icon" ] ) ;
                                      } else $image = BaseURLConcat ( 'Images/shop/icons/noIcon.png' ) ; 
                               }

Now it's when I get really confused! I'm not even sure what I have to do! If was normal ajax hover like just linking the image url I would be able to do but get from a db table I'm still not good enough to do! So If you guys could give me a tip or link me some kind of tutorial that I could learn I would really appreciated! I'm not here asking for you guys do it for me! I'm just asking for some light cos at the moment I really don't know what to do, I checked some links here on stack and I found that people use tooltipster I'm still trying to figure it out how to use the way I wanted!