I was lucky enough to have an iPad2 this last Christmas (thank youLinda) and I have really enjoyed using it.
Just recently I saw on the screen black square with rounded edges. Clicking on it brings up a larger black square with 4 symbols inset. Circle for gestures, star for favourites, white circle with small square inset named home
last a rectangle labelled device
I do not know how it got on to the screen but I should like to find out how to make it disappear.