Paint Pouring in a variety of ways has been around for a very long time, in the current form it has roots in the 1960's.
The aim of modern paint pouring is to use products (a pouring medium) to thin the paint down until it can flow well, then with additives and heat create distinct patterns with movements from a variety of tools.
A simple definition is: Acrylic Paint Pouring is the method of making acrylic paint flow in a variety of ways to create pleasing patterns that are usually abstract in nature.
The methods used for paint pouring when I started in 2017 had more focus about the pouring cup and using the movements to make things happen. As the art form grew in popularity there were a lot of additional ways to create, using basic household items, a variety of products to make the paint flow well and additives to help create cells, lacing, fractals and dendrites.
There were around half a dozen methods that were named, well known, structured and popular back then. In 2020 when a large majority of the world halted and turned to creativity and hobbies as an outlet, the named methods grew to around 50 or more, and in 2021 there’s at least 100 that I am aware of, and it’s constantly growing. It's a wonderful journey that's constantly being expanded on.
Personally I’ve done around 40-50 methods, some with greater success than others, and trialled a range of mediums, different additives, a variety of finishing products and explored a range of ideas.
This Art is generally considered abstract and is very forgiving once you have figured out the consistencies and ratios that work for you. The paint you use and the environment in your part of the world will impact how you do your mixes and pours, and may simply require some adjustments for great results. The greatest thing with this art form is the freedom to explore and express yourself in colour and emotion through the paint.