I'm basing this on my MA experience, but I think it's the same sort of picture for MScs:
Usually it's distinction, pass or fail - with distinction being comparable to an undergraduate 1st and pass being comparable to a 2:2. Sometimes there's a "merit" classification too, for people who do very well but miss out on the distinction - i.e. "high 2:1" type candidates.
Look carefully at the criteria for each classification on your course, as they can vary widely. For instance, you might need to get, say, 70+ overall to get a distinction, or you might just need to get 70+ on your dissertation or some specified proportion of modules and achieve some minimum standard on the rest.