HVLP : Stands for High Volume Low Pressure.
THey call the guns with the cups on top, top loaders
or gravity feed.
They make a couple of HVLP guns with the cups below like the old siphen feeds and work just as good. ( I used a matson for years till it wore out)
I know use a accuspray & an IWATA LVLP.

The old siphon feed guns required 45-65 PSI at the air cap ,there fore producing more paint in the air then on the car, this is called Volital Organic Compound , or VOC's.
The HVLP guns today require huge amounts of air supplied to the gun, but the air gets broke down inside the head to 7-12 PSI and it cuts way down on the VOC's in the air , so you have better paint transfer to the car being sprayed, which you use less materil today then of yesteryear.
I have used every gun type out there and can make them all work, they all have their quirks, just have to find one that you like , and it does go , the higher $ the gun , usually gives the best results., but that comes form someone that does it for a living, they do make some good cheaper guns
that do a good job for beginners & the home enthusiast, so it doesnt requir you to buy high dollar unless you use it everyday.
Hope that helped :-)
SprayTech
P.S.kevo , glad to help