Page Views: The number of pages visitors viewed on a given day. One visitor may visit three, ten, twenty, however many pages.
Unique Visitors: The number of individual visitors who came to the site. The unique visitors number should always be smaller than the page views number simply because one person can visit multiple pages and thereby generate a number of different pageviews.
Top Pages: The pages with the most visits. The page called "/" is the home page and it should get the most visits usually.
Search Terms: This shows which search terms visitors have entered in Google, Bing and Yahoo to find your site. The more search terms you see, the better ranked your site likely is in on the search engines.
Referring Sites: If a visitor clicked a link on another site to reach your site then they have been "referred" to your own site by this other site. The more inbound links you have pointing to your site, the better your search rank will likely end up being.