Multichannel Publishing means different versions of the content can be formatted for delivery in different physical "channels" like the web (HTML and PDF), traditional print, wireless handheld devices, and cell phones. Adobe calls it "network publishing."

The formatting is done using XSLT.

But another way to look at "channels" are different audiences or types of users which require a difference in the content, or perhaps only the presentation.

A major market differentiation is for multilingual versions of the content, which require Localization? (including both language translation and cultural modification of the content to suit the Locale?.

These are marketing channels, and in the extreme case of One To One Marketing? they require personalization of the content.