Besides the above, the Hubitat development environment is very similar to that of the "classic" (not the "new" model they will soon abandon this in favor of) SmartThings environment, which on the app side you can see here:
https://docs.smartthings.com/en/latest/smartapp-developers-guide/index.html
However, there are some differences, with this being an old (but it appear still relevant) thread describing most of them:
However, to be sure you're writing for the correct method signatures and other behavior, I'd also recommend looking at Hubitat's actual developer docs:
https://docs.hubitat.com/index.php?title=Developer_Documentation
The reason I'm linking to those last is that, unlike the ST docs, they don't really tell you how or when to use things; they mostly just document what some methods do, (ideally) the signatures of all, and leave it to you to know the rest.
That being said, this is a good a time as any to repeat my recommendation from above;
So try the stock apps first, consider Rule Machine (also takes some learning but isn't really custom code; there is lots of written documentation and examples, plus a couple videos), and try development if you want to--but I don't think you'll need to start at either of those last two places to get most of your automations.
Good luck!
