There are several key combinations to boot your Mac in recovery mode during start up. Depending on what you need to do with macOS Recovery mode these combinations serve different purposes.
Remember these options work on an Intel based Macs:
Command + R
Use this if you want to install the latest version of macOS that you had installed on your Mac (it won’t install a newer version if you hadn’t upgraded). Note that if you’re selling or giving away a Mac that is using OS X El Capitan or earlier you should also use Command + R – this will make sure that the installation isn’t associated with your Apple ID.
Option/Alt + Command + R
Use this if you want to upgrade to the latest version of macOS that is compatible with your Mac.
Shift + Option + Command + R
This will install the version of macOS that came with your Mac, or the one closest to that version if it isn’t available as a download.