A TMS sits between the order and the delivery: it picks a carrier and a route, generates shipping documents such as an EDI 214 status update, tracks the shipment in transit and checks the final freight bill against the agreed rate before it is paid. For a company shipping regularly, this replaces a set of phone calls, spreadsheets and manual carrier websites.
The common misconception is that a TMS alone fixes delivery problems. It gives visibility into where a shipment actually is, but someone, or some automation, still has to act on that information: rebooking a delayed load, notifying a customer or flagging a damaged delivery for review rather than letting it sit in a queue.