Tonearm/cartridge weight considerations


I have just decided to dig up my old vinyl collection that has been waiting for better days since mid-80s. Bought a turntable (Thorens 124) without tonearm. I have Shure V15V-MR cartridge. Started to look around for an appropriate tonearm and found out that the tonearm/cartridge issue has grown into a science. Now I am confused about this tonearm/cartridge weight issue. Could enyone illuminate me about this issue, mainly covering the following questions:
1) they speak of light/medium/heavy arms, so what are the figures for those weight categories?
2) are there weight categories for for cartridges and if yes - where my SHure V15V-MR fits?
3) does a light tonearm needs a light cartridge, or is it totally opposite - a light tonearm needs a heavier cartridge and vice-versa?
4) what can go wrong if the rules of tonearm/cartridge weight are ignored?
Thank you!
crockusbird
I suppose I missed the fact that there was no, "X" in his designation. The V15VX-MR has a compliance of 15. My bad! In that case: look for a fairly low effective mass arm. My Denon 103D's compliance is 30, and works wonderfully with my old Magnepan Unitrac I.
Actually the published spec for a Denon 103-D in 1977 was 12cu which makes it a medium, not high, compliance cartridge. See this link:

http://www.analogue-classics.com/html/denon_dl_103.html

Values of 10cu-20cu are considered medium compliance, 25cu high, and 35cu very high.

Hope that helps.
I don't remember saying my DL-103D was still stock. It now sports a van den Hul type I stylus, a boron cantilever and new rubber compliance. Tested as stated.
>>I don't remember saying my DL-103D was still stock<<

That's generally understood with cartridges; perhaps not electronics though.

New rubber, stylus, and cantilever aside, the significant increase in compliance over the stock specifications is doubtful. That's a big jump.