The line between 'tourist' and 'traveler' may be fuzzy and subjective, but it exists nonetheless and does its job of dividing extraordinarily well. As human beings, we tend to separate and categorize items in order to better understand the world in which we live.
There is a section of the book The Tao of Travel by Paul Theroux which highlights the distinction between tourists and travelers. While it seems obvious when directly presented with the separation, the delineation that Mr. Theroux makes is a digestible and effective touchstone to be used by both travelers and tourists alike.
Here are some quotes taken from The Tao of Travel that illuminate the differences:
'Tourists don’t know where they’ve been…Travelers don’t know where they’re going.' – Paul Theroux
'Travel is not a vacation, and it is often the opposite of a rest.'– Ibid.
'He did not think of himself as a tourist; he was a traveler. The difference is partly on of
time…Whereas the tourist generally hurries back home at the end of a few weeks or months, the traveler, belonging no more to one place than the next, moves slowly, over periods of years, from one part of the earth to another.' -Paul Bowles
Though, during and after reading his book, it seems as though Paul Theroux is a bit too inclined to promote his other works, his sharp insight into the state of the world voyager is well worth the read.
Many people who move about the globe began their journey as tourists and as their self-awareness/cultural consciousness increases they tend to evolve into travelers. Tourists may, in fact, simply be immature travelers and are therefore undeserved of the stigma attached to their moniker. Travelers, avoid regarding those glued to their guidebooks and itineraries with snobbery. Some people need to wade in the shallows before plunging into the shark tank.
So tourists will go to La Sagrada Familia in Barcelona because Lonely Planet or Rick Steves told them to, whereas a traveler might happen upon it while attempting to get lost in the city. Each person will experience Gaudi's unfinished masterpiece in their own manner.
The sin comes when travelers attempt to ingratiate themselves into the sticky reality of a new location, and end up disrupting their new found environs. The example of a bad tourist is one who looks for what they can take from a place, some item that they can show off to their friends and family back home to give an impression of superiority. The fault for both lies in a person's desire to serve only themselves as opposed to seeking to contribute, or anonymously observe some exotic location. The best tourist or traveler will almost always leave the people they encounter on their journeys with a positive outlook – quite to the benefit of future travelers.