First... I'm not a chemist, so this is just my understanding...
There are
chemical cleaners and
mechanical abrasives.
Chemical Cleaners
Chemical Cleaners would be a type of liquid that softens, dissolves or emulsifies. My guess is these would fall into the general category of what we call a solvent but it wouldn't be limited to solvents. Also remember water is a solvent, it will dissolve mud off a 4-Wheel Drive and water can also be an abrasive, it carved out the Grand Canyon. So don't be one of those people that has a knee-jerk reaction every time you hear the word solvent in connection with a product used on paint, it's not always a bad thing.
Mechanical Abrasives
Mechanical Abrasives would be any type of abrasive with the ability to abrade the paint when rubbed or worked against the surface. Mechanical abrasives can be placed it to 2 very general categories of Diminishing and Non-Diminishing but I'm confident the science behind abrasives is a lot more complex.
Here's a
weak analogy....
Goop Hand Cleaner, Lava Hand Soap
If you've ever worked on a car and got your hands dirty with the kind of black, oily dirt that penetrates into the pores of your skin, you may have used a soap like either Goop Hand Cleaner or a bar of Lava Soap to get your hands clean.
If you have then you know what I'm talking about, if you haven't then I'll explain.
Good Hand Cleaner is a Lanolin based hand cleaner, Lanolin is some kind of fat removed from Sheep, (I think, remember, I'm not a chemist). It cleans and removes grease from your hands by emulsifying it so it will then wash off.
Lava Hand Soap is a bar of hand soap but also includes Pumice particles which are mildly scratchy and they work to clean your hand by abrading dirt and grease off. It's more complex than I just described it because the Pumice works with the soap itself so you have a more complex cleaning action taking place than just abrasive particle being rubbed over skin.
