If you havent' already register your site in Google Analytics
https://www.google.com/analytics/web/
It takes 24 hours at least before you start seeing data and numbers appearing.
The data is broken into various types including Visitors and Unique Visitors
Pageviews is always the biggest number. It's the total amount of pages that were loaded. That's easy enough to understand.
Then you have two types of visitors. Unique Visitors and Total Visitors.
The total visitors is always higher. If someone visits your site 10 times in one day then you'd only have one unique visitor but you'd have 10 total visitors.
The way you know if these people have visited your site before is the percent of new users. Having 80% new users means 80% of the people have never visited the site before. Having only 30% of new users means people keep returning to your site regularly.
If you go to New vs Returning you can get information on the numbers of new visitors (the people who have never seen the site before) compared to people who have (returning users).
By clicking on New Visitors you can get the exact number of New People to see the site on any given day.
Hope this helps but if not ask for further clarification.