A plasma specialist was a type of physicist who specialized in the experimental investigation of plasma, such as in the fields of plasma dynamics or plasma physics.
Robin Lefler's parents were plasma specialists, who were, at one time, the only plasma specialists in the sector they were assigned to. As a result, the Leflers did a lot of traveling from starbase to starbase.
In 2368, Robin described, to Wesley Crusher the difficulties she had growing up because of her parents' profession, stating that "I felt like a piece of luggage after a while. I spent all of my time around technical equipment. My first friend was a tricorder." She later added, "my parents' work came first. They didn't really have time for me. Even when I needed them."
The loneliness she experienced growing up eventually led to the creation of "Robin's Laws". (TNG: "The Game")