Your conflict is represented in the game as a pair of story tags that you make up. Story tags are descriptors that characterize your hero, based on your conflict. For example, if you took the conflict The Ex-Soldier, you might create the story tags Tough as Nails, because you've seen armed conflict, and Eyes like an Eagle, because you were trained as a sharpshooter.
Similarly, your flaw also generates a pair of story tags, but these tags hinder you, so we often call these tags weakness tags. For example, if you took the flaw Disturbed, you might create the story tags Thousand Yard Stare, to describe your emotional detachment as a result of experiencing war, and Night Terrors, for the PTSD that troubles your sleep.
What's in a Tag?
Story tags are typically a short phrase that describes you succinctly, evocatively, and narrowly. A story tag should not be a simple adjective like "Resourceful" or "Bold" or "Clever": while these tags are succinct, they don't evoke any concrete image of you doing anything in particular, and they could be used in too many contexts. Consider tags like "Dumpster Diver," (you’re so frugal you can spot something useful even in a pile of trash) "Spelling Bee Champ," (it takes a lot of guts to stand up in front of the class and spell "sesquipedalian") and "Ex Con Artist" (which speaks to the specific ways that you’re clever). These tag are all evocative, narrow, and succinct.
Invoking Your Conflict
Before you roll, you may invoke each story tag once per session, by describing how they relate to some action you take. Add a +2 to your roll, in addition to any other modifiers.
Invoking Your Flaw
Before you roll, the GM may invoke each of your weakness tags once per session by describing how they hinder you in some action you take. This confers a -2 penalty to your roll.
Alternatively, you may invoke your flaw against yourself, in any of your rolls, to confer a -2 penalty (at the GM's discretion). You must declare that you're doing this before you roll. If you or the GM use both story tags against you in this way during a single session, you recover a fate point.
You may also invoke your flaw against yourself to create a GM Compel, rather than impose a -2 penalty on your roll. Invoking your flaw in this way is useful if there is no roll to be had for the situation. A GM Compel is an invitation from the player for the GM to step in and create a GM disadvantage that would hinder your hero or otherwise make them vulnerable. It can also be used as an inducement by the GM to get you to lean into behavior that's to your detriment.
For example, suppose you have the flaw Deranged, and one of your story tags is Sleepwalker. If you were harboring secrets you didn't want your hero to reveal to others, you could invoke your flaw to create a GM Compel that might encourage the GM to make you mutter those secrets when you're sleepwalking. Similarly, if you had the tag The Voices in My Head, the GM could have the voices tell you to do some terrible thing, and if you leaned into that GM Compel by doing what they voices say, it would count as having invoked your flaw.
The GM is not required to resolve things exactly as you describe, nor is he required to accept the compel if he thinks it does not create enough trouble for you to warrant banking a fate point. If he rejects your compel, you can try to invoke your flaw later in a different context.