The "Feature Info" (the box that appears when you click on a feature on your map) like most everything in your Maps site, is totally customizable! Here's how:

1. Open the LAYER ADMIN panel. 
   
2. Click on the layer for which you wish to change the feature info.
   
3. Click the "EDIT" button in the "Feature Info Pop-up" section of the layer edit screen.
   
4. Drag and drop fields to remove them or add them to the Feature Info. The list of fields on the right are the fields that will show to your users in the Feature Info Pop-up.
   
5. Click "Save".