A secondary dimension can be added to a normal dimension. This is an additional piece of information that provides context or detail. For example, if you are looking at a report on page views, you might want to know from which cities your page views are coming and thus add a secondary dimension of “city”. In other words, this goes deeper than just “the Netherlands,” for example.
You can easily add secondary dimensions to most reports in Google Analytics. You can select your desired dimension from the list by clicking on the “Secondary Dimension” drop-down menu. This will add a new column to the existing report, showing your selected dimension for each row of data.
Secondary dimensions can be helpful if you want a more detailed overview of the data in a report. But the same is true for answering specific questions about the data. For example, as a website owner, you might add a secondary dimension, “device type,” to an existing report on traffic sources. This way, you can see which devices generate the most traffic for your site.
Using secondary dimensions can help you better understand data in your Google Analytics reports.