Biker - Lives and breathes bikes. Could be riding anything but whatever it is they know every inch of it. Could probably tell you the minor facts and figures on almost any part of their bike/bikes.
Rides a bike - Owns a bike due to practical/economic reason. Generally doesn't even know what a sprocket is and doesn't care. Unlikely to do much "leisure" riding, their bike is just a-b transport. The amount of L plated scoots, peds and 125's around my area suggests to me this group is growing a lot.
Poser - Owns a bike because it seems cool/economic statement "look at what I can afford as a toy". Only brings it out for leisure and takes it places where it will get the most amount of stares. Knows nothing technical about their ride other than the sticker price, will chop it in for the latest attention grabbing model. Very important group as they ensure the supply of 2nd hand bikes.
Of course the above are terrible sweeping generalisations
