Treble was introduced with release of Oreo to hasten OEM release of OS updates. Questions pertaining to this should be used with this tag
Project Treble is for all new devices launching with Android 8.0 and beyond
Project Treble separates the vendor implementation (device-specific, lower-level software written by silicon manufacturers) from the Android OS framework via a new vendor interface.
In Android 7.x and earlier, no formal vendor interface exists so device makers must update large portions of the Android code to move a device to a newer version of Android
