In Google Analytics there is the possibility to display a second dimension for certain reports. An example: If I call up the entry pages report, I have the option of showing Google Analytics as a two-dimensional source/medium and can see for each entry page through which channels visits came to the page. Of course there are also other applications, e.g. in acquisition it would be interesting to be able to display the device type as a second dimension.
The example from the screenshot is different: the second dimension Medium is displayed here in the report landingpages.