Wi-Fi and Bluetooth chips are the chips that connect a phone, a laptop or another device to Wi-Fi networks and to Bluetooth devices such as earbuds, watches and car music systems. In most phones and laptops, one combination chip handles both. Wi-Fi is fast but covers a short range, a few tens of metres, and uses more power. Bluetooth carries less data, over about 10 metres, and uses very little power.
Both follow shared rules, so that any certified device works with any other. Wi-Fi follows a family of standards called IEEE 802.11. Bluetooth follows the rules of the Bluetooth group of companies. The page on connectivity standards explains why such shared rules matter. Wi-Fi uses radio bands at 2.4 GHz and 5 GHz. A Wi-Fi 6 phone close to its router can reach speeds of up to about 1 gigabit per second. Bluetooth uses the 2.4 GHz band, and its low-energy version uses only a few thousandths of a watt. That is why earbuds can play music for hours on a battery smaller than a coin.
Because Bluetooth and Wi-Fi at 2.4 GHz use the same band, and often the same antenna, the combination chip has to share it. Many times a second, the chip decides which of the two radios may send. It also has a small processor of its own, which runs firmware that handles these decisions without waking the phone's main chip.
Here is a typical case. A software engineer in Chandigarh works from home on a laptop. She is on a video call, with Bluetooth earbuds in her ears. The laptop's chip connects to the home's Wi-Fi router on the 5 GHz band, at about 400 megabits per second. The call needs only about 3 megabits per second, so there is plenty of room. At the same time, the chip sends the call's sound to her earbuds over Bluetooth, in small packets many times a second, and receives her voice from their microphones. Then she walks to the far room, and the laptop switches Wi-Fi to the 2.4 GHz band, which reaches further through walls. Now Wi-Fi and Bluetooth share one band. The chip gives Bluetooth its time slots first, so that her voice does not break up, and fits the call's video data into the gaps.
The other end of each link also needs a chip. In offices, it sits in Wi-Fi access points. A Bluetooth mouse or keyboard, part of computer peripherals, has one too. Smart plugs and sensors use smaller, cheaper IoT wireless chips, and smart speakers use ready-made voice assistant modules with these chips inside. The radio signals pass through the phone's RF front end on their way to the antenna.