Stock Android, also known by some as vanilla or pure Android, is the most basic version of the OS designed and developed by Google. It’s an unmodified version of Android, meaning device manufacturers have installed it as is.
The biggest advantage of stock Android is fast updates. Smartphones running it are among the first to get upgraded to the latest versions of OS, while owners of Samsung, LG, and other smartphones typically have to wait for quite some time to get an update. That’s because these manufacturers have to modify a lot of the software before they can release it, which isn’t the case with stock Android.
The second reason is that stock Android smartphones are bloatware-free, meaning they don’t come pre-installed with apps made by the manufacturer that you’ll likely never use.