A big mixing desk have a lot of channels that you can record and/or mix through. Usually these channels have a preamp, an EQ and sometimes a dynamics section (I.E. a compressor). A channel strip is basically one channel that could’ve been pulled out of a mixer. Home recording have had a great impact on what kind of recording gear is available today. Many of us only need one or two channels to record at once, and possibly a nice compressor to even the levels as we do it. With that said, channel strips are probably more popular and common than ever before. So instead of buying a separate compressor, mic preamp and EQ, the channel strip allows you to have it all in one box.