Just my opinion, but I've always felt the "traditional" golf swing involved shifting the weight to the back foot on the backswing and then to the front foot at impact and on to the follow through. It also involved allowing the left heel to come off the ground to allow MORE of this weight shift on the backswing. I think the old Scots and Brits who were the first "teachers" promoted this b/c they were playing all bound up in tweed jackets, etc., and lifting the left heel allowed them to turn further. This became the accepted swing used by Bobby Jones through Snead, Hogan, Palmer, Nicklaus etc. Look at videos of all those guys, and at the top of the swing they're up on their left toe with the heel off the ground....some more/less than others.....
The "modern" swing is just what Scotts33 describes, and involves keeping the left heel on the ground, coiling the upper body, while resisting with the lower body. When I learned to play I lifted the left heel and for years had a helluva time with timing the downswing. If you were late shifting your weight back to your left foot you'd hit it left....if you were early shifting the weight you'd hit it right (at least those were MY experience). When your timing was perfect, you'd hit it straight. Somebody (Jimmy Ballard maybe?) figured out that keeping the front heel down on the ground helped you hit it straighter. At least, that's the way it has worked out for me. I've lost maybe a little distance swinging with my front heel down, but I've become more consistent that way.
Again, this is just my opinion and how it's worked for me. A good teaching pro would probably shoot holes in my version of the swing.