Grebs claim to be the individuals of society, and although they all dress fairly similarly, they are the minority, so I suppose they're right. Most grebs listen to rock or punk music. The greb crowd tends to have a layered structure, with the upper echelons consisting of those that have been grebs the longest: they have attained the enviable status of "old school". Those that have just arrived on the greb scene are known as "newbies", and tend to be viewed with some contempt by the old school crowd. Newbies have to go through a period of piss-taking before they are accepted as proper members of the greb community; this is a kind of hazing ritual and gives the new greb a chance to see what they will have to endure from chavs. After enough time has passed, these newbies become old school, with a wave of newbies stepping in to fill their place. Grebs tend to be more accepting than other groups of people, such as chavs, and generally nicer. They also don't use words such as "bare" or mug people, which is always a good thing.
Those guys in black with skateboards that hang around not doing a lot and being friendly but unproductive.