This is a detailed review, definitely a solid place to start learning about macOS High Sierra.

Before you update, you might want to read the section on APFS, the Apple File System called A one-way ticket to APFS-ville (if you have an SSD).

The High Sierra installer does do one major thing that the Sierra installer didn’t do. Behind the scenes, it converts your boot partition from the longstanding HFS+ filesystem to the new APFS.

Well, it does that for most Macs, anyway.

Though most people will never even know what’s happening, there are plenty of caveats and details to know about how the APFS conversion happens, the cases when it doesn’t happen, and why it doesn’t happen when it doesn’t happen.

Read this section, consider your Mac’s particular configuration. Do you have a spinning hard drive? Do you have an SSD that you installed yourself? Do you have a Fusion drive setup? None of these are dealbreakers, but it’s worth spending the time to read about these cases before you do the upgrade.