Jesse Clark explains the traveling salesman problem:
One of the canonical questions in operations is the traveling salesman problem (TSP). In its simplest form, we have a busy salesperson who must visit a set number of locations once. Time is money, so the salesperson wants to choose a route that minimizes the total distance traveled. It is not so hard to imagine these path optimization problems occurring within warehouses where people (‘pickers’) need to navigate aisles and fill orders as they go.
The Traveling Salesman Problem is a computer science classic and acts as a classic graph optimization problem. Check this post out for more details.