New Visitor vs Returning Visitor

Technological amnesia

Most analytics tools rely on cookies to establish whether a visitor has been to your website before or not. In the case of Google Analytics it 'records a visitor as 'returning' when the _utma cookie for your domain exists on the browser accessing your site'.

This is great. It means you get metrics like % new visits sent to the site over a given time period and allows you to understand any differences between the two groups.

http://www.periscopix.co.uk/blog/ive-never-been-here-before-or-have-i-how-to-analyse-new-and-returning-visits/