Android M meaning in Softwares ?

Android Marshmallow (codenamed Android M during development) is the sixth major version of the Android operating system and the 13th version of Android. First released as a beta build on May 28, 2015, it was officially released on October 5, 2015, with the Nexus devices being the first to receive the update.

Marshmallow primarily focuses on improving the overall user experience of its predecessor, Lollipop. It introduced a new permissions architecture, new APIs for contextual assistants (first used by a new feature "Now on Tap" to provide context-sensitive search results), a new power management system that reduces background activity when a device is not being physically handled, native support for fingerprint recognition and USB-C connectors, the ability to migrate data and applications to a microSD card, and other internal changes.

As of August 2021, less than 5% of Android devices use this version, and when it was warned that a billion users use this (or older) version, by then no longer supported with security updates, was when 40% used those versions. Since then at least 70% of the users of those old versions have upgraded to a newer version.