While the most basic version of Android is AOSP, from 'Android Open Source Project', the version of Google is this: Android Stock. It has the Google Apps pre-installed, and with Google Play services, but it does not have any type of bloatware nor does it have a customization layer. It runs the core Android kernel as it was designed and developed by Google, then it could be considered as 'base' from any other version.
Smartphone and tablet manufacturers mostly take the Android source code from Google and they modify it. The modifications they carry out serve to provide compatibility to their hardware, but also to introduce changes in design at the interface level. And to add functions through own apps. This is what is called the customization layer, and we have a good example in Samsung's One UI. Or a fork, which are even larger modifications, as is the case of Xiaomi's MIUI for its mobile devices.
The differences and main advantages of Stock Android over versions modified by manufacturers
En Android Stock there is no bloatware, that software not necessary for users that comes preinstalled on the device. Therefore, on a device with Stock Android we have a storage space greater in relation to what was promised. If the device has 64 GB, for example, the storage space real and available It will be higher in a Stock terminal than in one with a customization layer. But also, due to the simplicity of the software, and the scarcity of modifications, the most common thing is that a device with Stock Android receives the updates in a faster way.
Many users prefer Stock Android because not having bloatware also means, in most cases, a higher performance and greater autonomy. In addition to a simpler and, at the same time, customizable design. However, what Android Stock does not have are precisely the advantages of a version customized by the manufacturer. Meanwhile in Android One There are, although few, some apps from the manufacturer, in Android Stock only the ones are pre-installed. gapps or Google Apps.
Obviously, on Android Stock you can also make modifications with a launcher, or with root to make system-level customizations. The operation, as a base, is identical to that of a version of Android modified by a manufacturer.