Flax is the name for both the natural bast fiber used to make linen, and the plant from which it comes. Flax’s use as a fiber dates to 30,000 years ago (These Vintage Threads Are 30,000 Years Old, NPR.org).
To obtain the soft fiber from the stem of the flax plant, the woody stalk must be removed by retting.
The flax plant, Linum usitatissimum, is used not only for its strong, soft fiber, but for its seeds, and the various parts of the plant have long been used to make linseed oil, rope, paper, medicine, soap and dye, as well as fabric.