Answering questions from the Week 5 Preparation task
TF2 makes affordances visible through the use of a class system. Each class has been balanced differently and can be quite useful in some situations, not so much in others.
Each class has different weapons and abilities, for example... The soldier class can rocket jump by simply jumping and firing a rocket under their feet to propel themselves higher in the air to reach cliffs/ledges that were unable to be reached prior. What this allows is a different style of play and much more opportunities for classes to be played.
Just like every other First Person Shooter, players are constrained to the map's borders and are forced to play the objective.
Payload is a gametype where a team has to escort a bomb that is on rails (It can only move forward & back) to the other teams base. During all this, the other team is engaging the bomb and effectively pushing back the attackers.
Payload gametype in Team Fortress 2
TF2 encourages players to play the objective since that is the only way your team can win Payload.