Several questions about scenery files

1.Although I've been simming for a number of years (1996 I think !) I've never really understood how the scenery library works in FS2002 and I've noticed some simmers recommend making different folders for different sceneries. What's the advanatge of this and how should I go about it please ?2.In my FS2002 folder I've got a folder caled 'SCENERY' (capitals) and one called 'SceneryDB' - what's this second one for ?3.if you move from area to area during a flight, does the right scenery get moved up the scenery file library list so that the one you want is at the top, and why would you want to disable a particular scenery file ?Finally 4. What's the difference between 'mesh' sceneries and what's AFCAD files all about ? Does adding a mesh scenery add anything to the FS default scenery at all ?That's a lot of questions and I'd really appreciate a few comments or advice where to read up on it please.Many thanks in advance to anyone who can spare the time to respond.PS I did load up FS 1998 the other day which I remember being very impressed with at the time - yeuk and double yeuk !!