A good way to start learning about scripting is to follow along with an example project.
Start with the unity roll-a-ball tutorial. I find unity’s other official tutorials of this type not to be as helpful; there is a lot of scaffolding and such to ignore (where did these assets come from?) just to show basic concepts, but if you’re itching to get making something, check them out.
Your hub for unity’s official tutorials on scripting: here
Scripts are just text files. They are assets in our project. We can think of scripts as components. When we write a script, we are making our own components, adding our own behavior and functionality.
We almost always need to write our own scripts in order to create games – you can’t get by without them, but we don’t often need all that much complexity, and frequently can avoid doing advanced things.
Q: Which should you use?
Unity doesn’t support UnityScript anymore, and if you see that term it means you are looking at something out of date. Ignore it completely.