“Channel” is a generic term to describe a group of indicators with upper and lower lines. It can include things like the traditional “MA Channel” but in some trading platforms there’s a built-in category of indicators called “Channel Indicators” which includes things like Keltner Channels, Bollinger Bands and Envelopes, too.
So different people use these terms with different meanings. Channels and ribbons, also.
I don’t think any of these things was what @ria_rose was referring to, though! 