Tim W gurgled happily, sounding much like they were
saying:

A wifi router is set to a channel and can work fine to one laptop. Add
more machines and they are all in contention on the same channel.

Yes.

Not quite.

A network is set to a channel.
That network shares a maximum theoretical bandwidth - 54mbps or whatever
- between the entire network. Think of an old-style hub, rather than a
switch.

Where the channels become an issue is when there's multiple networks
within reach. All of the channel frequencies overlap their neighbours
slightly. Get too much traffic on an overlapping frequency, and your
connection can get a bit flaky.