Short answer: Wi-Fi is two-way radio. Your router and devices send data as radio signals in a few bands that anyone may use without a licence. How well it works depends on distance, what’s in the way, and how many other devices are sharing the same airwaves.
Radio in shared bands
Wi-Fi uses unlicensed bands set by regulators. In the US, the FCC rules define the 2.4 GHz band as 2400-2483.5 MHz and set power and radar-detection rules for the 5 GHz bands. In 2020 the FCC also opened 1,200 MHz at 5.925-7.125 GHz, the 6 GHz band. “Unlicensed” means shared: your neighbours’ networks, Bluetooth and even microwave ovens use some of the same spectrum.
Bands and range
Each band trades range for speed. Lower frequencies reach further, so 2.4 GHz has the longest range, while 5 GHz and 6 GHz are faster but cover less. Modern routers broadcast on several bands at once. See Wi-Fi bands explained.
Walls and interference
Signals weaken with distance and with whatever they pass through. In NIST laboratory measurements, drywall, plywood and glass absorbed relatively little, while concrete absorbed the most. That’s why router position matters so much; see where to put your router.
Channels and sharing the air
Each band is split into channels. Devices on the same channel take turns to transmit, so a channel is shared airtime. The 2.4 GHz band is crowded: Cisco notes it has only three non-overlapping channels in the US, 1, 6 and 11, while 5 GHz offers many more. See Wi-Fi channels explained.
Standards and generations
The technical standards come from the IEEE’s 802.11 working group; the Wi-Fi Alliance certifies products and gives the generations their names, mapping Wi-Fi 6, 5 and 4 to 802.11ax, ac and n. The newest, 802.11be (Wi-Fi 7), was approved in September 2024. See Wi-Fi standards explained and Wi-Fi 7 explained.
Security
Because anyone nearby can receive the signal, Wi-Fi encrypts it. WPA2 has shipped on every Wi-Fi device since 2006, and WPA3-Personal adds protection against offline password guessing. See WPA2 vs WPA3.