Google starts rolling out Android 6.0.1 Marshmallow updates (only to Android One handsets for now)
It's not clear exactly what Android 6.0.1 is bringing, but it's definitely a minor update, likely including bug fixes. What we can say is that this isn't related to Google's monthly security updates, since the November security patch has already been released - without changing the Android version number (all recent Nexus devices, including the new Nexus 5X and Nexus 6P, still run Android 6.0).
HTC ROM developer @LlabTooFeR has it that, after 6.0.1, Google is planning to roll out Android 6.1 Marshmallow, though this is expected to happen starting next year. Needless to say, Android 6.1 should be a more important update compared to 6.0.1.
sources: Reddit, @LlabTooFeR via Android Beat