Hi, Adam. Drywall, or gypsum board is made of gypsum board in a paper envelope. Gypsum is a naturally occurring mineral. It is mixed with water, kind of like plaster to which it is related, in a slurry. Paper is formed into a wide "U" shaped trough and the slurry is pumped in and it flattens and another piece of paper is put on top. Then it is heated to dry it and the slurry hardens. Since the length could be as long as how much paper is on a roll, it is cut to length.
Wallpaper is just good quality paper that is printed. Glue is applied to the back, sometimes. Other things, like vinyl to improve water resistance, can be applied to the front. Historically, the glue is basically flour and water but other things are added for improved properties or more modern chemicals are used.
Since both materials are paper and water will melt the glue, you should apply a sizing or primer to the wallboard to increase the water resistance of its surface. Otherwise, when you strip the paper, the paper surface wallboard could be harmed.
You might want to search the web if you have further interest. There will, no doubt, be a lot of info available on these subjects.