Absolutely nothing. There I've said it. In some circles there seems to be a debate about whether to call yourself a traveler or a tourist and in many cases it's because someone who considers themselves a traveler frowns upon the term tourist. So let's define the terms.
A tourist travels for pleasure and recreation. Their stay is usually not more than a year before returning home. Perhaps he is just there to soak up the culture, see the sights, participate in a sporting event or two, or even visit family and friends. His trip is usually planned out with points of interest to see or places to visit. Tourism is the bread and butter of many countries. They rely on tourists for the major part of their income.
Travelers on the other hand are those who set out with no particular plan. They may stay in one place for a period of time, even a few years, and then travel on. The intention is to travel--move from place to place as the verb suggests. While they often visit the important places of interest in an area, they don't usually plan all of it. I think we've met some people in our dive trips that I would label travelers. There are a lot of dive masters who travel from one part of the world to another, stay a few years, work in the area and explore and then move on.
Too many times someone will want to consider themselves a traveler rather than a tourist just based on the fact that they shun the usual tourist attractions. What a shame. Those very attractions offer glimpses into the history and culture of an area. Sure we laugh at some of the ways famous places have become "tourist traps" but that doesn't necessarily take away from the importance of seeing them or experiencing the history and culture that surround them.
I don't mind being labeled a tourist. I like coming home, touching base with friends and family and then planning for the next trip. You see, I've always maintained that a good part of the fun of traveling is in the planning and anticipation. And who wants to miss out on the Eiffel Tower, the Coliseum, the Grand Canal, La Segrada Familia, or Big Ben? Not me!