In the top left-hand corner of your reports, next to the full audience or segment name, there is a 'Compared to' option, which allows you to compare the audience and segments against a baseline of your choice.
When you are viewing the insights of the full audience, the default baseline will be a ¨Global¨ Audience OR if the audience is made up mostly from one country, the default baseline will be that country's national average (users within that country who are also on Twitter). If you clicked on one of the Segments to enter the report for the first time, the baseline will automatically default to the Full audience (comparing the Segment against the rest of the audience to show what is unique, special about the segment in question).
You can select the baseline you would like to compare the audience to at any time or on any tab. This could be a country, to which you can also add gender; for example, you could compare your audience to the female UK population (depending on your original definition or the demographics findings in the report).
Every time you create an Insights report, the Full audience analysed and the Segments identified automatically become baselines you can choose from. You can find these on the left-hand side of the baseline menu.