Most obvious, and perhaps most useful for a novice, the help function provides the information on a given value type, function, or other entity. Let's get meta and see how the help function works by itself. If you type help(help), this is what you'll get in VS Code (press q to exit):
In Jupyter, there is a similar built-in command—the question mark (?). Here is an example using a question mark in Jupyter—help?:
Generally speaking, help provides a longer description and works everywhere, but the question mark works on variables as well.
In the most recent versions of JupyterLab (versions 1 and above), you can open a window called Contextual Help next to your code. Once opened, the window will show the documentation for the closest function or variable automatically.