Why are there 11 channels in WiFi communication instead of 3? I'm a little confused about subdividing the WiFi radio band into 11 channels in the USA, 14 in Japan, and 13 in Europe, and to then use just 3 of them because of the overlapping problem. Why didn't they subdivide the band into 3 channels?

IEEE 802.11 (Wi-Fi) uses the 2.4 GHz ISM band that existed decades before IEEE 802.11 was defined, and the band was divided into 5 MHz channels.

Wi-Fi uses 22 MHZ bandwidth, more bandwidth than a single 5 MHz channel in the ISM band provided. The required Wi-Fi bandwidth does not map directly to a single channel and overlaps multiple channels, but Wi-Fi devices can pick any of the ISM channels as the center of the bandwidth it uses, overlapping on channels either side of the center channel chosen. It boils down to three center channels that do not overlap for Wi-Fi.

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