The chain stitch allows the sewing and the oversewing to be managed in the same process. The first stitch to be mechanized, thanks to Barthélemy Thimonnier, it was replaced by the lockstitch on most sewing machines because of its lack of solidity: pulling on the end of the thread would unravel the whole seam. It remains nevertheless appropriate for stretchable fabric. It uses only one thread, unlike the lockstitch, which uses two.
The caption reads in the original French:
Point de chaînette.