As a player, you create a character for the Universe that you play in. You take control of that character with the following rules and interactions.
Aside from acting as your character, your main mode of interaction with the game as a player are Skills, Powers and Traits. These are actions you roll for in situations where using your character's capabilities are relevant.
A Skill is a concrete, learnable capability from the Universe you play in. They can range from mundane faculties available to everyone to specialized qualifications that require intense training. Examples: Deduce, Charm, Sense.
You choose some Skills you want your character to be good in, and roll with dice whenever you want to use that Skill. more on that later!
Traits are special rules that add more gameplay variety to how you play your character. You can see it as a way to add a more personal touch to how your character interacts with Skills and resources. Examples: Scrappy, Comforting, Meditative.
The rules are quite varied but usually, it revolves around resources you get in specific situations or can spend to do something extra.
A Power is a collection of strong abilities with its own ruleset that requires expending resources to use. Generally speaking, you spend Focus to activate powered abilities, but some Powers might have their own resources or requirements instead. It's possible that the Universe you play in does not have any Powers, either because they don't fit the setting or because they add too much complexity to the rules. Examples: psychic powers, magic, ninjutsu, and tactical combat maneuvers.