What is the difference between LNAV/VNAV and LPV minimums on an RNAV approach?
There's an FAA paper on RNAV approaches that explains the differences between LP, LPV, LNAV and LNAV/RNAV approaches. I made a table for my own reference but since StackExchange doesn't allow tables (AFAIK) here's a summary:


LP: no vertical guidance; WAAS required; MDA for minimums
LPV: vertical guidance; WAAS required; DA for minimums
LNAV: no vertical guidance; WAAS not required; MDA for minimums; requires RAIM integrity if WAAS is not available
LNAV/VNAV: vertical guidance; WAAS or baro-VNAV required; DA for minimums; requires RAIM integrity if WAAS is not available (i.e. if using baro-VNAV); possible temperature restrictions if using baro-VNAV


The difference between LPV and LNAV/VNAV is that although they both have vertical guidance, LPV was intentionally designed to be very similar to an ILS approach with an increasingly sensitive glideslope whereas LNAV/VNAV was not. Other answers have additional comments about LNAV/VNAV having been designed earlier and for different equipment which would certainly make sense.