How do WiFi channels work on dual-band routers?



I understand the high level stuff about router channels (e.g., too many devices on a channel can cause interference and impact data transfer resulting seemingly slow internet connections, 2.4 GHz bands has 11 channels, 5 GHz bands have 45, etc). However, I’m not understanding the low-level technicalities. From what I could find online, WiFi router channels are dividends of the the width of a wave length. And typically 2.4 GHz band is divided into 20 MHz widths, which I suppose makes sense if you posit 2.4 GHz = 2400 MHz total bandwidth, divided by 11 channels resulting in roughly 20 MHz channels, but how or what is dividing it? How can a router determine what data is coming on what channel? Does the router keep track of channels similar to an ARP table? If there are different channels why is there some overlap?

Edit: changed a word.

In: Engineering

Chanels in the 2.4ghz band are spaced 5mhz apart. Given their 20mhz width, this is why adjacent chancels are overlapping.