Both supported editors for the micro:bit have handy reference documentation to help you code.
Python Editor
Selecting the Help '?' icon in the menu on python.microbit.org will open a set of links.
Documentation will open the MicroPython for micro:it reference material with examples of python code to use in your programs.
Help will open the editor help page.
Support will take you to support.microbit.org for any additional help you require.
MakeCode Editor
Selecting the Help '?' icon in the menu on python.microbit.org will open a set of links.
Support will take you to support.microbit.org for any additional help you require.
Reference will take you to the MakeCode for micro:bit reference material.
Blocks will take you to the blocks language reference material.
Javascript will take you to the Javascript reference material aimed at more advance users.
Hardware will take you to information regarding the micro:bit device itself.