a difference between Watercolor, Oils, and Acrylic? What a silly question you ask. Well yes, there is...it is the medium itself. When you paint in watercolors, you are using a pigment that is mixed with a substance called gum arabic, which is the binder. The gum arabic comes from the Arabic tree so it is a natural component. There are other common additives, like glycerin, humectant, extender, dispersant, and water. Some use more additives, like two or more pigments and also maybe a brightener.
In Acrylic paint you also start with pigment and
a synthetic resin binder, The acrylic also has additives of Surfactants, to disperse the pigment, anti-foaming agents to stop the paint from frothing. Cheaper paints also contain things that are cheaper than the pigment, like dyes, opacifiers, and fillers. Acrylic paint also has lots of mediums for various things like thickening the paint, keeping it wetter when painting in Plein air....and lots more, too many to list.
Oil you ask? Well of course it has pigment....and pigment for any of the types of paint can be from natural things like rocks and plant extracts. The binding medium is linseed oil. The viscosity of the paint can be modified with turpentine or white spirit, and varnish can be added for the glossiness of the dried oil paint.... and lots of other things, also too many to list.
These are the basic differences, but then we add the drying time of the finished painting. Watercolor: very fast. Acrylic: pretty fast, depending on the extra mediums you use. Then Oil: some say oil never really dries, but it does, it is just the slowest of the paints to dry.
Then there is the cleanup...
Watercolor is just soap and water on brushes. (I only use soap on my brushes after quite a few paintings as the paint readily washes off in my clean water jug.)
For Acrylic you must keep brushes in the water at all times, so the paint does not dry on the bristles, while you are painting. You must always clean brushes with soap and water after each painting. and you must clean your palette each time as well.
The oil clean up is a little more time consuming. First, wipe off as much paint as you can, then put your paint thinner (there are a lot of different kinds) in a jar, and rinse your brushes in it and then wipe them down again then rinse in warm water ....then repeat the paint thinner process until the paint is gone. This may take quite a few rinses with paint thinner to be sure all the paint is gone. Then you must use a bar of soap to make a lather and continue to do this till there is no evidence of paint. Sometimes you may have to use commercial paint cleaners to continue this. Then dry in a flat position. ( all brushes should be dried flat.) Important: Keep all of your Oil supplies away from small children.
Before you need to clean up, you still need to know how to mix a color, make a composition, all the important things I teach you in my classes! Like how to have a much easier cleanup. Oh, and when painting in Plein Air with watercolor you only need paint, a brush, paper, and water....simple!
I am all for a simple clean up and to have as many natural ingredients as possible. It started many years ago when my then 5-year-old daughter put her cute little finger through many an oil painting checking to see if they were dry. I needed to change from those slow drying, smelly, toxic oil paints. (Remember, that was about 45 years ago and the oil paints have changed somewhat.) For me, the fast-drying, easy cleanup was the key to my love for watercolor.