generally refers to the type of food you would find at a pub, bar, or any place of the like. In America it tends to be sandwiches, burgers, salads, appetizers, and sometimes entrees.
"Let's eat here at Joe's Bar and Grill, it's pub fare."
"What the heck is pub fair?"
"You know, sandwiches, burgers, stuff like that. And it's fare, not fair, dummy"