Mick,
The very best way to understand is to see one in action, but I'll try to give you a basic idea. I'm referring to a bowl gouge here, NOT a roughing gouge. The difference is that a roughing gouge is ground straight across and has "right-angled corners," whereas a bowl gouge has more of a nose, usually with the sides sloping back slightly (depending on original grind or preference). The problem you're having sounds like it could be caused by the trailing corner contacting the work.
When you look at your bowl gouge from above, with the flute (inside of hollow shaft section) uppermost, you'll see the cutting edge at the business end. Turn the gouge over to see that the bevel (the sloping section directly below the cutting edge) is angled - this angle varies quite widely, but all that matters for now is that you identify it.
With your workpiece mounted, position the toolrest slightly below centre and parellel to the face of the bowl, quite close to the workpiece without fouling it.
With the lathe OFF, place the underside of the gouge on the toolrest and lower the handle until you can get the bevel flat on the wood, around one third of the diameter of the workpiece in from the front. Keep the gouge in contact, then gently turn the workpiece BY HAND and you should NOT get a shaving, as only the bevel is in contact.
Now, with the workpiece stationary, rotate the gouge slightly to the right (clockwise), examining the bevel whilst you do so. Note how the attitude of the gouge now needs to be altered slightly to keep the bevel in contact, because a different part of the cutting edge is now "in play." Again, turn the workpiece gently BY HAND and continue to lift/rotate the gouge until you JUST begin to take a shaving. That is the cutting edge working in a bevel-supported cut.
The gouge can be used in this way quite effectively and you will find that you'll need to rotate it quite a way over onto its side in order to keep the cutting edge supported by the bevel as you get deeper into the bowl. You must NEVER cut past the centre of the bowl, otherwise you will come into contact with "rising" wood and most likely get a monumental dig-in. However, you can start from the center with the gouge rotated anti-clockwise, pulling it towards you. Try this, again rotating the workpiece BY HAND.
If you over-rotate the gouge, then the trailing edge can get involved, which is usually quite a surprise! Also, remember to watch the shaft of the gouge against the side of the bowl, as this can cause some unexpected and fairly damaging results too!
Once you get the hang of what part of the tool actually does the cutting and realise that the cutting edge needs to be supported (behind the cut) by the bevel - or at least a part of it - you should begin to make progress. I haven't explained this very well, but I hope that it's given you an idea of the way it works. I've found that I understand stuff better if I know why as well as how. If you can get a copy of Kieth Rowley's "Foundation Course" book or video, this will do a far better job of explaining things.
Ray.