To access the recovery menu, at boot hold down the Command + R until the menu has appeared.
In the recovery menu, you can select multiple options and tools.
If you would like to reset the device:
If you do not know the password and cannot recover it. At boot hold down Shift + Option + Command + R until the computer prompts you to install Mac OS. Then follow the prompts.
This will install the OS version that came with the device or the closest one available.
If you want to install the newest OS, then hold down Option + Command + R at boot until prompted.