Explain.
Well.
http://www.erowid.org/plants/cannabis/images/archive/hashish12.jpgIt's not actually resin, it's just what it gets called. It's Hashish, but well, it's not very good, hence the price.
The stone is very, very lethargic. Feels like there's no THC in there whatsoever, all just cannabinols.
It also makes you hack and cough like a dying cat if you smoke much of it, so as a student, when it's all you can afford and you smoke a half ounce in a night, you know about it.
There is speculation as to what they put in British hash. Scientists have claimed that it is leaf matter, as expected, although you would then expect that to only be padding out the resin. They reckon it includes coffee powder and shit to colour it, and everyone I know reckons there is tobacco in it. I don't think that makes sense since it would raise the price over something nastier, but I have noticed that it seems that way when you quit smoking.
Anyway, it's best avoided. You can buy proper resin over here (Squidgy Black) or Charisse, which is the resin with buds crushed into it, which is a fine smoke, but green is becoming far more prevalent of late.