I've recently become the proud owner of a 1938 home which needs quite a bit of work. I am hoping to do most of it myself. I recently looked under the thin carpet that covers the entry way... and this is what I found. I eventually want to tile the entry way, but I have no idea what this stuff is, if I need to remove it before tiling or just go over it. Although it is cracked, the pieces seem to be glued down, and I wasn't able to remove them. So, what do you think this is?