An additional widget you can add to a dashboard for more specific analysis.
An additional metric you can add to a report for more specific analysis.
An additional dimension you can add to a report for more specific analysis.
A visualization that allows you to understand the impact of your data.
Explanation: Secondary dimension actually let you analyze the report more specifically.
What are the secondary dimensions?
To explain what secondary dimensions are, we need to explain what dimensions are first. I’ve written a post about dimensions (and metrics) in which you can read that:
A dimension is a description, a characteristic, a feature or aspect of your data. It’s not a quantitative variable but more a qualitative variable.
So, it’s quite often letters instead of numbers. Let me give you a concrete example: in Google Analytics’ reports, the first column of the table is always a dimension:
In this case, ‘Country’ is a dimension. Now, what you can do, is click on the first country you see in your reports. This will take you to a more specified report about the country you’ve clicked on: you’ll see regions. Now, these regions can sometimes be clicked on as well. That depends on the country. If you want to see cities, you can add a secondary dimension. Here’s how:
For More Details: https://yoast.com/secondary-dimensions-in-google-analytics/