THE MacOS recovery has existed since the release of OS X Lion (10.7). The feature is part of the recovery system integrated with the Mac and is available, so you can run the utilities to recover the computer in case of certain software problems.
When you want to do a clean reinstall of the operating system, for example, by macOS Recovery. But why am I saying this? For a simple reason: no macOS Sierra 10.12.4, Apple implemented a small but important change in the behavior of the feature.
Before, by pressing the R keys during system startup, you could re-install the macOS installed on the Mac. For example: if you have a Mac running OS X El Capitan (10.11) and press those keys when starting the computer, you can, among other things, reinstall El Capitan itself.
By pressing the R combination, you open Internet Recovery, which makes it possible to restore your Mac to the original operating system that came with it. If you have a MacBook Pro from mid 2015, for example, it came with OS X Yosemite (10.10); When reinstalling the system using Internet Recovery, you will have access to this version of OS X macOS again.
Now, with the release of macOS 10.12.4, Apple has changed that as informed by Thomas Brand. Here's what she says:
MacOS Recovery installs different versions of macOS depending on the key combination you press during startup. Press and hold one of these combinations immediately after pressing the power button to turn on the Mac. Release when you see the Apple logo or a rotating globe.
- A: Reinstall the latest macOS that was installed on your Mac, without upgrading to a newer version.
- A: Upgrade to the latest macOS that is compatible with your Mac.
- A: Reinstall macOS provided with your Mac or the closest version of it still available.
Changes in the behavior of the first two key combinations described above and this new combination (R), of course, are only available to those already running macOS 10.12.4.
Undoubtedly, Internet Recovery has now become much more convenient by giving you the option of upgrading to the newest version and compatible with your machine; at the same time, it's cool to see that, at least on macOS (since iOS doesn't work like that), Apple still allows us to install older versions of the system which came factory installed on computers.
Apple support articles in Portuguese that address the issue (About macOS Recovery and How to reinstall macOS) are not yet up to date with the new behavior implemented in macOS 10.12.4. So, in case you need any instructions, it is better to follow even the English versions of the documents (About macOS Recovery and How to reinstall macOS).