The two sort of base liquids that everything (nicotine & flavors) get mixed into.
You can make
juice out of either or from a blend.
MORE flavorings come in or mix-into PG, so it's more common to start with that - but some people are allergic, and look for ALL VG juices, and they're out there.
When ordering something that comes with blend options, you can consider that more PG may mean more Flavor, and more
Throat Hit, while more VG means thicker
juice, and more Vapor. So people have different preferences.
I hope that PLAIN ENGLISH is close enough to accurate, and helps a little!