Sublime text is a customizable UI text editor.
Its main functionality comes from user-created plugins written in Python. These plugins can provide anything from syntax highlighting for a programming language to full LSP support.
There is a helpful Guide/Reference at https://docs.sublimetext.io/. Here are some helpful pieces of information I will likely have to look up in the future that I learned from that Guide/Reference.
You can discover the names of commands that are issued as you use sublime text by opening the console and doing some things:
Once you've pressed Enter, any and all commands that are issued as you use sublime text will be logged in the same console window.
There is no official command reference, and some commands are simply hidden within the editor. However, there is an incomplete list in the Reference linked above.