You have the definition there on that page. KL uses 17 different fare classes grouped into several families such as "Business", "Economy Fully Flex", "Economy Semi Flex", etc.

The individual letters have, of themselves, no real meaning. You can tell the basic features of such a flight from this letter, but not all the details. They exist merely to allow the airline (and all airlines use a similar system) to set various price points and sales restrictions within each of these broad families via the fare basis code, which usually starts with this same letter. It is the full fare basis (not the fare class) that has a meaning of the type you seem to want. The letter only allows you to see what "family" your ticket has and what mileage earning applies. It has no further meaning.

For instance, a fare basis VNLSAT may refer to a "V" ticket for departures from the Netherlands and requiring a Saturday night stay. A fare basis VDEAPEX may refer to a "V" ticket for departures from Germany with a very restrictive advance purchase requirement. (These are fictitious examples. Very often the fare basis contains no clues as to what sort of restrictions apply to the fare. But usually the first character indicates which of the single-letter fare codes that sector will be in. It is the fare basis that contains ALL details about the ticket and these can be looked up to obtain the sort of information you seem to think you can get just from the "V". This letter gives just general information such as that shown on the page you linked to. But for the full, specific details, you instead need to find the fare basis. There can be several different "V" types of ticket that could be sold even in a single market, all at potentially different prices)