A pescatarian is someone who is a vegetarian, but also eats fish. That is me.
A few other caveats: as a nice Jewish guy, I don't eat un-Kosher fish. So, no shellfish, bottom-dwellers (catfish, etc...), shark, eel, anything that is not a "true" fish. It has to have scales and fins.
I know, I know. Lobster is amazing (so people tell me, at least, since I have never tried it). Scallops look fun. Eel is one of my friends' favorites when we go out to sushi. Sorry, guys. I have never had these things, which probably makes it a bit easier not to eat them, since I don't know what I am giving up.
Why don't I eat meat? I keep Kosher, which means that any meat I would eat needs to follow certain guidelines. If a mammal, it has to have cloven hooves and chew its cud, so no pork, rabbit, or the like. (Apparently, giraffe was recently ruled Kosher, but I don't know a single restaurant to serve it.) It needs to be killed in a certain, more humane way. It can't be a reptile or amphibian. And more to the point, it can't be mixed with milk products. This is an issue. Butter and cheese are the two things I cannot live without, with apologies to my wife. Hence, it is MUCH easier to just not eat meat, and not worry about any of the rest.
The thing I have found is that very few people realize that not eating meat does not mean not eating well. I eat very well, and my wife and friends say I cook very well. I hope through this blog that you see that a pescatarian can eat just as much, and just as well, as anyone else. Just not at many steakhouses.
I hope this helps a bit. Enjoy!