Returning and first time traffic
When someone comes to your site there are two possibilities : either that person has never been to your page before or he/she has come at least once in the past (whether a few hours ago or several months ago). In the first case, we speak of first time traffic (it's the first time the visitor ever sees your site), in the second case, we speak of returning traffic.
First Time Traffic Graph: The background of this graph shows the total daily or monthly traffic on your site. Superimposed in pink is the daily first time traffic.
Returning Traffic Graph: The background of this graph shows the total daily or monthly traffic on your site. Superimposed in blue is the daily returning traffic.