A "visit" is the session of activity for one user on a Web site during a fixed time-frame (including all hits). A unique user is determined by a unique IP address or cookie. By default, a user session is usually terminated when a user is inactive for more than 30 minutes (although this duration can be changed).
A "new visit" is defined as a first visit made by our chosen individual (or IP address or cookie). A common misconception in Web analytics is that the sum of the new visitors and the repeat visitors ought to be the total number of visitors. Here is the culprit: There is really no such thing as a new visitor when you are considering a website from an ongoing perspective. If a visitor makes their first visit on a given day and then returns to the website on the same day, they are both a new visitor and a repeat visitor for that day. So if we look at them as an individual which are they? The answer is both, so the definition of the metric is at fault (something the online advertising research industry needs to address).
Nobody expects the number of first visits to add to the number of repeat visitors to give the total number of visitors. The metric will have the same number as the new visitors, but it is clear that it will not add in this fashion. If on the day in question, there was a first visit made by our chosen individual, and there was also a repeat visit made by the same individual, then the number of first visits and the number of repeat visits will add up to the total number of visits for that day.
NetLingo Classification: Online Marketing