LPV
"Localizer performance with vertical guidance"
You can only use an LPV approach with a waas approved GPS and RAIM is available, you must make sure that your gps shows i believe it says LPV on the display
Your basic GPS approach is an LNAV and then if it has a VNAV and you have vertical guidance available and showing on the HSI then you can follow that down to your minimums.
You use the VNAV mins if they are listed and you have vertical guidance showing. A simple answer is when do you use loc mins and when do you use ils mins....when the glideslope is not available. Or of course if your equipment is unable to provide vertical guidance such as inop equip.
Reference this article.
https://www.faasafety.gov/files/gsla...20JulAug06.pdf