Originally Posted by
ajax
Buses generally conduct short-haul trips and are not primarily designed with the comfort of the passenger in mind. They are usually part of an integrated public-transport network and their stops are far more frequent than what would be found on a coach network. Usually transport costs the same when traveling within a particular zone, regardless of destination. Busses can be hailed and stops can be requested when on board.
Coaches generally conduct longer trips, are designed with more of an eye towards the comfort of the passenger and are part of a fleet run by a long-haul coach company. When purchased, tickets are always to a specified destination. Megabus and National Express are two very ubiquitous British examples. Coaches themselves are outfitted in a manner similar to Greyhound busses.
And of course, with every good rule, there are plenty of crossovers and exceptions - the
Stagecoach X5 service near me is one of many hybrid bus/coach services. OTOH, Megabus have been known to use painfully uncomfortable ex-HK buses for their coach services.
It's not just the service, either, it's the vehicles themselves. A coach will typically be designed to travel long distances at higher speeds, and will normally have a raised seating area, with luggage storage underneath (although not necessarily - there are double-decker coaches with lower-level seating, yet visually, they're easily identifiable as coaches).
However, as the sign at the entrance to Edinburgh Waverley station used to say "Training is better then Coaching"...