system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how does Bluetooth work?

Explain like I'm a 5 year old wondering how Bluetooth actually works and is able to connect two devices to each other. I get that it's some sort of signal but what actually is happening?
gpt
Bluetooth is rather just a name for a kind of wireless technology that focus on lower power consumption rather than bandwidth (speed) or range. It occupy the ISM band (2.4GHz), same as Wifi. It modulates its signal with PSK(Phase-shift keying) based scheme. 

Basically the two device that communicates through BT technology first negotiates using a set of protocol. Once an agreement is reached (pin is correct, protocols version is compatible, channel to use, encryption keys etc.), the two device would then be paired (connected), and further communication can be carried out.

A BT device wish to transmit (and all wireless technologies that uses a protocol in general) would broadcast a modulated carrier signal with encryption (optional) that was negotiated upon pairing. And all BT device listening to the channel (a wireless frequency, say 2.4125GHz, channel 1) would accept the message provided it was deemed to originated from the paired device, otherwise the message would be ignored.

On a even more basic level, a BT device wish to transmit converts your message to binary bits and a wireless chip would modify a carrier signal (a commonly recognizable wave, a radio wave that would repeatedly go from high to low and back at a fixed rate.) so when the radio wave is captured on another BT device, by comparing the radio wave received to a known wave (carrier), it would figure out what message the other BT device was trying to send.