Generic name, e.g. mensshirts.org.uk, relates exactly to a product or service, usually has exact match search volume on Google.
Brandable, either completely made up name, e.g. navito.co.uk, or perhaps something like haroldsmensshirts.co.uk. A term that needs "branding" by advertising for people to be able to recognise and remember.
Then perhaps also the "generic brandable", e.g. lowprices.co.uk. Might have some search volume and be an understood term, but can also be branded through advertising.
Rgds