The difference is of course notoriously difficult to define, and can lead to some acrimony, particular by some revivalists who get ratty when someone else says they prefer traditional folk music. But. difficult to define or not, surely anyone without cloth ears can tell the difference.
   Listen to, say, a recording of Joseph Taylor, Leadbelly, the crowd at Padstow, Bob and Ron Copper, and a Rumanian village wedding band. Your ears will tell you these very different musics have a quality in common. Then listen to recordings of traditional folk material arranged by Vaughan Williams, or Benjamin Britten, or the Kingston Trio, or Faitport Convention, or Martin Carthy. You are listening to something else. Anyone can detect these differences. The first category I would call traditional, the second revival.
   Defining the difference is tricky, not least because anyone can think of challenging borderline cases (as with all classification systems). I take care of the awkward in-betweens by saying it is possible (though perhaps unusual in England) to be a traditional and a revival performer at the same time. And of course, you can play rock'n'roll and classical music as well if you wish, also difficult to define but easy to recognise.