Reporteur is a simple reporting tool for your Google Analytics account. It analyzes the live data from Google Analytics API and summarizes it in WP.
They represent the pageview data coming from Google. Not unique pageview. Just pageview. So if someone visits your website 2 times in a month and looks at a total of 10 pages it counts as 10 pageviews.
They represent the visits data coming from Google. Not unique visitors. Not absolute unique visitors. Just visits. So if someone visits your website 2 times in a month it counts as 2 visits.