Chatter is a free, private, security-first texting device.
It comes in a pair because texting yourself is not as fun as you think.
Unlike your regular phone, this device does not need a cellular network or a SIM card to work because it creates its own wireless network and communicates with other Chatter devices you've paired it with.
It uses the so-called “LoRa; low-power wide-area network technology in order to send text messages, emojis, memes, and GIFs.
Chatter uses a publicly-available set of frequencies that are allocated for use cases like this one.