Lugs are those tiny protrusions on the face of the watch case that hold the strap or bracelet in place. They are the supporting component of the structure of the watch. The strap is held secure due to these lugs. Lugs can be quite creative, from straight and angular to curved and tapered, and in many cases, they integrate well with the overall aesthetic of the watch.
The lug width refers to the distance between the lugs and defines how large a strap the watch is going to be able to accommodate. Beyond their functional purpose, lugs also enhance the comfort and fashion elegance with which the watch sits on the wrist.