It is an old debate, it is a recurrent topic you can discuss with fellow travelers, and it can lead to heated debate. Yet for others, there is no debate at all, as they don't see a distinction in the first place.
Still, I would like to make a small contribution myself to the eternal Tourist vs. Traveler debate. I will state from the start that I do believe there to be a difference between the two. I realize the distinction is a purely subjective one, but to me, that does not mean that it is not something that can be talked about. Actually, I think the debate is interesting precisely because the topic is so personal.
I feel that a tourist is a person who, generally speaking, has the following traits. He organizes his travels, and preferably books his hotels, trains, etc. ahead, and makes a precise plan for his time in a foreign country - more often than not, a short time - perhaps a few weeks at the most. It is entirely possible that the tourist takes an organized tour and travels in a group of people he doesn't know. A tourist is interested in seeing many things in a short time, and is less interested in connecting with the locals in the country he is visiting. The tourist does not like risks, and prefers to stay on the safe side. He is fine attending a dinner with local dance performances, and although he might try some local dishes, he secretly hopes they will be adjusted to his own taste. For accommodation, the tourist is likely to stay in pretty good hotels. Of course, doing all these things, the tourist prefers to use a guide, who speaks his own language if possible.
The traveler, on the contrary, loves travel because for him, travel means adventure. Freedom is very important to him, and that in itself is a reason for the traveler to never book anything ahead - or if unavoidable, as little as possible. Instead, the traveler believes that travel is all about taking the unknown path, see where it leads to, and be surprised by the outcome. The traveler does not meticulously plan his stay in a country, but has an open-minded approach where he leaves a lot to destiny. For the traveler, travel is about meeting locals, trying to connect, to savour the country in all its aspects. In order to do so, we could see the traveler try local dishes that might look appalling and that he would never even think of touching at home, we could see him struggle with a language guide, just like we could see him try hitch a ride on a local car. For the traveler, travel is inevitably linked to suffering, at least to some degree. The traveler will hardly, if ever, stay in a fancy hotel, will take local transportation where he might end up with a chicken (or worse!) on his leg, and will generally try to sort things out himself. Only if not otherwise possible, will he resort to using a local guide. He might organize to travel with other foreigners he meets on the way, just for fun. Often, the traveler has a lot of time on his sleeve, although this is not necessary.