M2 has an "XBEE compatible form factor socket" on the top of the processor board. In other words: two 2mm pitch x 10 pin headers spaced 22mm apart. Read more about XBEE modules here:
Of course there are LOTs of modules that fit this socket, with many different functions. WIFI, BLE, GSM, LTE, ETHERNET, etc.
This page will show how to interface various modules and get your M2 talking to the CLOUD.. woo hoo