Processing is a language for creative coding.
Processing is an amazing tool with which you create sketches, or small code projects that do all sorts of fun things. You can create games, or artworks, or tools that connect to extenal devices, or visualisations, or generate animations or ANYTHING!
Go browse the sites below to get a flavour of what can be done.
Note: Processing is the older Java-based version of p5Js Javascript-based version. Processing is better at working with local files, such as generating videos, or loading arbitrary data, p5js is better for web projects. They are both very similar, I would recommend exploring both.
The OpenProcessing site is a gallery of the amazing projects that have been made with Processing and p5js.
(Slightly confusingly, p5js is the modern Javascript version of Processing. Processing itself is java-based)
Not only is this site inspirational, you can also view the source code, and remix any project you like to develop your own version.
First, you need to download Processing.
Loved by data scientists and artists, this editor lets you code fabulous things
Dan is an amazing teacher, who will teach you all you need to know about Processing. Follow his tutorials and you will go from the basics to really complex and amazing projects in no time.
Whenever working with Processing, it's always a good idea to have the Reference window open.
The Fun Programming site builds up your learning using lots of simple, runnable code examples. Brilliant.
A vibrant community of learners, enthusiasts and experts are there in the forum to help yoiu with Processing or p5js.