The M.2 WWAN module requires to be integrated with a host system in order to be functional and provisioned with connectivity via a service provider (MNO or MVNO) SIM card.
The ingredients in the host device include M.2 WWAN module Hardware, Antenna, Firmware, Host OS Driver & Application/Service.
In order to get a proper overview, these are the key areas:
(1) The host interface (hardware/firmware/OS software) that exposes to the end user & integrator.
(2) Services: Cellular connectivity, Telephony services, SIM, Positioning technologies.
(3) Internals of the Hardware, Firmware, Host OS Driver Structures.