In this Gamasutra opinion piece, writer and designer Gregory Weir (The Majesty Of Colors) examines the complex appeal of Team Fortress' character classes and how they support gameplay.
"The concept of character roles in video games is a common one. It's most common in traditional RPGs, where the player chooses a certain character class with unique skills and abilities.
In the mid-to-late-nineties, the concept of class or character role spread to other kinds of games, with one of the first examples being the original Team Fortress mod for Quake.
The Team Fortress series features first-person, multiplayer, team-based gameplay where each player selects a class and the classes compliment each other. Each class has an important role, and the strength of the team as a whole depends on each player properly fulfilling their role."