[yodameister]

Here is a snippet from wikipedia that helps explain the difference:

Some Star Trek enthusiasts prefer the term "Trekkie", while some others self-identify as "Trekker". Self-identification as a "Trekkie" became even less popular after a famous national television parody in 1986 (see Parodies below); several self-described "Trekkers" were quoted as saying they "had a life" (contrasting themselves from "Trekkies").

In the 1991 TV show Star Trek: 25th Anniversary Special, Leonard Nimoy attempted to settle the issue by stating that the term 'Trekker' is the correct one.

In the documentary Trekkies, Kate Mulgrew stated that Trekkers are the ones "walking with us" while the Trekkies are the ones content to simply sit and watch Star Trek.