Definitely a convenience store, and the kind of dirty look, dinghy fluorescent lighting that makes you want to grab your stuff and leave. However, it is convenient for a beverage, some chips, chocolate -- a snack place and some quick items you might need to get for dinner but don't want to go out of your way if this place happens to be right there.
I will agree with some other Yelpers that the guy manning the register was not rude, but looked completely miserable being there, and robotic in ringing you up. I can only imagine the young guy was a relative of the owner and got stuck working there on a Sunday for crap pay, otherwise a half smile or a nod of goodbye would have been appreciated. At least that way, even if the store and selection was "meh", a customer would want to come back knowing the owner or staff was happy for the business.