Are you trying to this update on a specific device, or A/B (seamless) system updates - Android Open Source Project
If the update in partition B fails to boot or is buggy, the system automatically reverts to partition A. This prevents the device from becoming "bricked" during a failed update process. AB-GOTA.zip
The most interesting feature regarding this file format is its capability: Are you trying to this update on a
These packages often contain only "differential" data, meaning the file size is much smaller because it only includes what has changed since the last version rather than the entire operating system. AB-GOTA.zip