What kind of paper did monks used?

Answer 1

By the 12th century, parchment and paper were in use. Very early they would have used products like parchment and vellum.

Parchment is a writing material made from specially prepared untanned skins of animals-primarily sheep, calves, and goats. It has been used as a writing medium for over two millennia. Vellum is a finer quality parchment made from the skins of young animals such as lambs and young calves.

Answer 2

Monks used parchment, which was made from animal skins, particularly from sheep, goats, or cows. Parchment was durable, smooth, and suitable for writing by hand. Eventually, paper made from plant fibers became more common.