ArsTechnica has a in-dept article covering new version of the mobile operating system: Android 8.0 Oreo, thoroughly reviewed. My highlights from that article are:
Project Treble introduces a "Vendor Interface"—a standardized interface that sits between the OS and the hardware. As long as the SoC vendor plugs into the Vendor Interface and the OS plugs into the Vendor Interface, an upgrade to a new version of Android should "just work.
So you should get Android updates faster as long the vendor provided firmware is still supported. Google decides which version it will support based on data collected (how many devices are still on that version).
ROMs shouldn't need to be painstakingly hand-crafted for individual devices anymore—a single build should cover multiple Treble devices from multiple manufacturers. Imagine the next time a major new version of Android is released. On Day One of the AOSP code drop, a single build (or a small handful of builds) could cover every Treble device with an unlocked bootloader, with a "download Android 9.0 here" link on XDA or some other technical website.
Also graphics driver can now be updated through Play Store like any other app.
The Great Background Processing Lockdown
Apps can't just run in background using CPU, RAM and battery as they want. With Oreo they are required to show a notification saying that they are doing background work so you get to decide if an app is doing too much or not. Also, some events will not trigger background processing for all apps like before, making the UI more smoother. And to prevent apps for consuming the battery, all the background processing work will be done through a scheduler in batches, allowing phone to "sleep" more to preserve battery.
Old blob style emoji are being replaces with something that looks closer to iOS emoji and we get 69 new emoji and all skin options. To improve compatibility, developers can use EmojiCompat library and then we will not have to wait for Android updates in order to stay up to date with emoji. This will make sure you will see correctly all emoji and app developers can even chose to replace OS emoji with Google provided one (Samsung, LG and other manufactures overwrite default Google emoji with their custom ones).