I have already posted a snippet about beeswax some time ago, when I had freshly made my blocks of wax. So here is the version for "All the gory details":
Beeswax is still used for sewing today, sold especially in quilting shops as a little helper for waxing threads for easier use. Drawing the thread over the surface of a beeswax block will lightly coat the thread surface with wax, protecting it from abrasion by the needle eye. Simultaneously, any surplus twist from the plying and winding process is removed from the thread, much reducing its tendency to develop kinks and tangles. Especially linen threads profit a lot from waxing.
Use of beeswax in textile work is documented for medieval times through different written accounts like inventory or acquisition lists. Rests of organic matter identified as wax were also found on pinked edges of cloth, sealing the cuts in their crisp, neat appearance. There are no finds of wax pieces in context with sewing - but like most organic matter, beeswax will quickly decay in the ground.
Beeswax was also used to protect the edges of a cutout embroidery on linen before sewing it into place, or to waterproof linen. That, of course, will use more beeswax than just waxing the threads.
The wax offered here is produced from modern bees (of course), of very high quality and very clean - wax of similar quality is often used in cosmetic production. The wax comes in blocks that were made using modern equipment.