Important: The flavor of something is from a combination of chemicals. That flavor you experience isn't just from the taste of something. It's also from the smell and even the color. Multiple senses are involved.
That concept comes into play when flavor chemists (flavorists) do their magic. Some of that magic is trial and error or chemical analysis.
Natural flavorings are extracted from "real" things. Fruit, vegetables, roots, seeds, seafood, etc. There are multiple ways to pull the flavor out of something. Let's say through heat and/or enzymes and/or biochemical reactions. Sometimes that extraction doesn't require a lab. Example: Vanillin comes from vanilla beans, and you can extract it by letting it hang out in ethanol (booze) for a while. If you want a more concentrated flavor, you just "boil" off some of the ethanol.
Just because a flavoring is natural doesn't automatically mean it's safer. The natural extract of almonds has traces of cyanide in it. Also, the artificial flavorings can be cleaner/have less impurities, and have to go through more testing. (But really, is anything ever tested enough to be 100% safe? Nope.) Fake flavorings are cheaper. They don't require growing fields of food first. The massive problem is that artificial flavors can be quite inaccurate. Strawberry comes to mind.
Artificial flavorings are chemicals combined together to mimic a flavor you're familiar with. That means the lab people have to make sure the chemicals also produce the right smell (see above).
One random chemical is butyric acid. It's found in animal fats. It stinks. Creating it is a process of its own.
Butyric acid and butanol react together and create butyl butyrate. That smells like pineapple. Allyl hexanoate can be used in pineapple flavors, but can also be added to other flavorings, like peach.
So in one sentence...
Your flavors come from a lab and might be created with a complex recipe using ingredients you can't get at the grocery store.
Side notes:
1. Some artificial chemicals are considered safe to eat and are also used for vaping. And as you know, vaping is a big unknown.
2. Just because a chemical is natural doesn't mean it's safe to vape. There's a giant debate over the dangers of vaping natural oils.
3. People tend to hate on things they don't understand. They might assume something's not safe just because it has too many syllables. You have to know enough to realize when people are talking nonsense/uninformed/basing conclusions on partial info.