What is the difference between unique visitors and number of visitors?

The total number of visits is the total number of visits during a given period (usually 1 month). Out of that total visits number, unique visitors is in this total.

For Example: Total Visits = 1000 / Unique Visitors = 500

Therefore you had 500 visitors who came back twice each to the website. This is a rough example and does not take into account that 1 visitor could have been back 10 times, another 3 etc.

Under the Total Number of Visits on the AWSTATS tracking system it gives the average visits per user. The higher this number the better it is for your website.