Definition:
Unique visitors represents the number of visitors to a web site with a unique IP address, domain name, cookie or a combination of all three in a given period (most commonly 30 days.) This is probably the most important web site statistic to watch.

Total number of visits, page views and hits are all driven by the number of unique visitors to a web site. This statistic when combined with other statistics will also provide an accurate view of how visitors view your web site. A much higher number of visits compared to the total number of unique visitors could mean that visitors find your web site useful and return for updated information frequently. The opposite of this scenario may indicate great search engine optimization but a lack of compelling information.