Respondent funnel shows you the number and percentage of respondents who have clicked, segmented, subsegmented (if applicable) and converted in the campaign. The respondent funnel can be found within the Performance tab of all portfolios, campaigns, creatives and traffic sources.
The below screenshot comes from a specific creative's respondent funnel. In this example, 21 total respondents have viewed this creative over the last 30 days. 10 respondents have "segmented," meaning they clicked a tagged action. 10 respondents "subsegmented," or clicked a second tagged action. 10 respondents in this creative converted within the last 30 days.