What did weavers do in the middle ages?

They were people who took fibers like wool and made it into threads so it could be woven to make a woolen fabric.

2nd answer: Actually, the above process is spinning, not weaving. Once fiber has been made into thread it is woven into a fabric on a loom. This is the job of the weaver. The cloth from the loom then goes through a process called fulling in which it is cleaned and thickened and then stretched on a frame. Fullers, also called walkers because part of the process involved pounding the fabric, which was done with the feet if a water mill to drive hammers was unavailable, were a separate profession. It then goes to a dyer, and then is ready for sale to the public.