What's the difference between a tugboat and a towboat?

When pushed by a boat, the barges are referred to collectively as 'the tow,' hence the term 'towboat.' This term is potentially misleading, since such boats actually push their cargo, as opposed to literally towing it or pulling it from behind. Tows can also be pushed by a {tugboat;} the difference between the two is that a tugboat has a pointed bow, while a towboat or pushboat has a square bow which can face up flush against the tow.

tugboatenthusiastsociety.org/pages/tugboats-and-towboats-01.htm no longer exists
http://www.louisianafolklife.org/LT/Articles_Essays/creole_art_big_river_trad.html