The Travelling Salesman Problem (TSP) is often misunderstood regarding its classification; it is NP-hard, but the decision version of TSP is NP-complete. Verifying if a given route is the shortest can be done in polynomial time, which is a key aspect of NP-completeness. The distinction lies in the fact that a problem is NP-hard if it can be used to solve an NP-complete problem in O(n) time. The discussion emphasizes the importance of understanding the decision version of TSP to grasp its complexity classification. Combinatorial optimization remains a compelling area of study due to these complexities.