The original IEEE standard was the 1 and 2 Mbps of 802.11, which ran at a frequency of 2.4GHz, as do almost all the many later variations on 802.11. 802.11b was the first upgrade, it runs faster, at 5.5Mbps and 11Mbps, but still at 2.4GHz. It uses a spread spectrum technique. Range is 100 or more metres. The Wireless Ethernet Compatibility Alliance (WECA) certify 802.11b compatibility and allow use of the WiFi (Wireless fidelity) brand name.

The 83 MHz wide 802.11b band uses 11 channels of 22 MHz wide, so only 1, 6 and 11 do not overlap. You can change the setup on each WiFi card so they use the same channel, if it turns out someone else nearby is using the default channel.
The denser the population, the more likely this is. As at 2003, it looked like WiFi had won the radio connection battle, with a variety of much better priced products, even faster variations, and a lot of support.

Note that WiFi is inherently insecure, especially as delivered.

• 802.11a isn't compatible, as it runs at 54Mbps and at 5GHz. It has 12 non-overlapping channels.
• 802.11e is intended to be backwards compatible with both a and b.
• 802.11f is intended for roaming between multiple wireless access points.
• 802.11g speeds up 802.11b to 54Mbps, but stays at 2.4GHz.

You should also note that most IEEE 802.11 (WiFi) wireless LANs also operate in the same 2.4 GHz band as Bluetooth, however Bluetooth's design makes it likely that it will not be as subject to interference as WiFi. The 2.4 GHz unlicensed band is used by all manner of industrial equipment, including household microwave ovens and cordless phones. Interference is very likely as the density of devices increases.