The eyeball   When you use a module to the left of the “Save and Exit” you will see an icon that looks like an eyeball.  If you click it (takes a little time) you will see how your page looks on a computer screen, a tablet, and a cell phone.  This can be handy specially to see how a photo will look. 

Also, always remember to name you module.  At the bottom where is says “Admin label” leave the type of module but add a short description.  By doing this you can easily find the module you need from among many on a page.