Need to replace tire on Dahon folding bike I bought a Dahon Vitesse D8 two years ago and it's lasted extremely well so far. Recently, the rear tire got a puncture and as my tires both looked pretty worn, I thought it might be time to look into getting replacements. 

I was looking to get some tyres for cycling on roads and occasionally on gravel/canal paths. but I'm now a bit overwhelmed with the amount of tyres available. Could anyone suggest what I should be looking for in a tyre?
The Dahon Vitesse D8 site says it ships with


  KOMMUTER, 20" x 1.75"


tires.

Any tires of those dimensions will do the job.

The applications you mention suggest that a tire with a small amount of tread would be better than a slick (no tread) tire.

The mind boggling array of tires you see is because the suppliers are all trying to distinguish their products, when they all do pretty much the same job.

I recommend taking your bike to your LBS and fit whatever tires they suggest, provided they have tread.