A braid is a conducting envelope that encloses a wire or cable and may perform many functions – some electrical, some mechanical. The primary electrical function is to prevent interference with surrounding wires or electrical components by confining the electrical signal within the wire or cable.
This protection also guards your wire or cable from outside electrical signals and interference. Medical and aerospace applications are particularly susceptible to outside interference. Mechanically, shields are used to protect the wire from physical damage, like abrasion.