It could just be a type of pad. I have seen some that look like foam board but are flexible. Most likely it can be removed. It may have some staples in it but should remove easily. Pray it isnt glued or something dumb like that. i would say go for it.
Recently we did a show where we talked about an easy technique for refinishing hardwood floors that are not in too bad of shape. Maybe give it a listen if ya want.
Its here Old hardwood floors, repair and refinishing