Vaporwave is a different genre from synthwave. Synthwave is based off synth-heavy 80s music, especially action and thriller/noir movie soundtracks. If you watched Stranger Things that has a very synthwave sound track.
Vaporwave is more sample based and is traditionally about looping distorted samples of 80s/90s songs, though it branched out a lot. Personally I'm a fan of naturewave, which is looped and edited "nature" or "new wave" sounds. But, key difference, it normally doesn't use a lot of classic synth sounds.
Retrowave I think refers to the over all aesthetic genre; so vaporwave and synthwave both fall under retrowave.
Vaporwave is more sample based and is traditionally about looping distorted samples of 80s/90s songs, though it branched out a lot. Personally I'm a fan of naturewave, which is looped and edited "nature" or "new wave" sounds. But, key difference, it normally doesn't use a lot of classic synth sounds.
Retrowave I think refers to the over all aesthetic genre; so vaporwave and synthwave both fall under retrowave.