The Fight skill covers all forms of close-quarters combat (in other words, within the same zone), both unarmed and using weapons. For the ranged weapons counterpart, see Shoot.
Since you don’t really use Fight outside of a conflict, it’s not often used to overcome obstacles. You might use it to display your fighting prowess in a demonstration, or to participate in some kind of regulated bout or sport fighting, which would allow you to use this skill in a contest.
Create an Advantage:
You’ll probably use Fight for most of the advantages you create in a physical conflict. Any number of special moves can be covered with advantages: a targeted strike to stun, a “dirty move,” disarming, and so on. You could even use Fight to assess another fighter’s style, spotting weaknesses in his or her form that you can exploit.
This is self-explanatory. You make physical attacks with Fight. Remember, this is for close-in work, so you have to be in the same zone as your opponent
You use Fight to defend against any other attack or create an advantage attempt made with Fight, as well as pretty much any action where violently interposing yourself could prevent it from happening. You can’t use this skill to defend against Shoot attacks, unless the setting is fantastical enough that you can catch missiles or swat them from the air or use laser swords to deflect blasters.