The Athletics skill represents your character’s general level of physical fitness, whether through training, natural gifts, or genre-specific means (like magic or genetic alteration). It’s how good you are at moving your body. As such, it is a popular choice for nearly any action-y character.
Athletics is all but ubiquitous among every genre appropriate for Fate—it would only be unnecessary in a game that focused exclusively on interpersonal interaction and had no physical conflict.
Athletics allows you to overcome any obstacle that requires physical movement—jumping, running, climbing, swimming, etc. If it resembles something you’d do in the decathlon, you roll Athletics. You use overcome actions with Athletics to move between zones in a conflict if there’s a situation aspect or other obstacle in your way. You also roll Athletics to chase or race in any contests or challenges that rely on these types of activities.
Create an Advantage:
When you’re creating an advantage with Athletics, you’re jumping to high ground, running faster than the opponent can keep up with, or performing dazzling acrobatic maneuvers in order to confound your foes.
Athletics is not meant as an attack skill.
Athletics is a catch-all skill to roll for defense in a physical conflict, against close-quarters and ranged attacks. You can also use it to defend against characters trying to move past you, if you’re in a position to physically interfere with whoever’s making the attempt.