Individual, smaller sections of the overall frequency band used by a wireless network
Any one network segment where one computer can interrupt another
Using switches can reduce collision domain. Switch remembers in which physical domain a specific computer lives. MAC table.
Wireless devices don’t have physical cables. This is where channels comes in.
When we say 2.4 GHz, it really mean that they operate on roughly the band from 2.4 gigahertz to 2.5 gigahertz between these two frequencies are a number of channels, each with a width of a certain megahertz.
For 802.11b network, channel 1 operates at 24.12 megahertz. But since the channel width is 22 megahertz, the signal really lives on the frequencies between 2.401 megahertz and 2.423 megahertz. This is because radio waves are imprecise things so you need some buffer around what exact frequencies a transmission might actually arrive on.
Channel 1 is always completely isolated with channel 6. This mean for 802.11b network, channels 1 and 6 and 11 are the only ones that never overlap at all.