Embarrassed -- but I have to ask

Have been a member of this site for over a year now and a long time lurker prior to joining --- it is a truly great site, I have learned lots along the way, and in a funny way become addicted to it, the endless supply of queries [and answers] entertain and inform.
However I appear to have missed something, I have searched and searched but cannot find the answer --- underneath every user name is row of six aircraft, which appear to be highlighted from the left depending on some criteria? The user names are also linked to various travel names [New passenger, Road warrior, Frequent flyer etc]
Can someone put me out of my misery and explain the significance of these [are they linked to the number of posts?]-- I am sure it must be on the site somewhere and probably discussed many times before but after looking for several months I am embarrassed to say I give up - help!
However I appear to have missed something, I have searched and searched but cannot find the answer --- underneath every user name is row of six aircraft, which appear to be highlighted from the left depending on some criteria? The user names are also linked to various travel names [New passenger, Road warrior, Frequent flyer etc]
Can someone put me out of my misery and explain the significance of these [are they linked to the number of posts?]-- I am sure it must be on the site somewhere and probably discussed many times before but after looking for several months I am embarrassed to say I give up - help!