Wall paper is a decorative paper used to cover dry wall when you redo a room in your house. Wallpaper can also be a border allowing you to make a stripe.
this is a good question, paste should be kept to the back of wallpaper by using all the paste table. when you paste wallpaper you should lay it on the table so the joining edge is right on the edge...
You can Hang wallpaper over wallpaper but it tends to not hold to the walls as well as hanging in on a bare surface. However, if you must, first paint over the old wallpaper with an oil-based paint....