What does “il s’agit de” mean in French?

Il s’agit de means “it’s about,” “it’s a question of” — and it has no usable subject. That il is a placeholder, like the it in “it’s raining,” so the thing being discussed can never move to the front: ce film s’agit de… is simply not French. You say dans ce film, il s’agit de…, or reach for the easier ce film parle de….

It conjugates like any other verb, which is where it gets elegant: il s’agissait d’une erreur (“it was a mistake”) and, in the mock-formal register this clip enjoys, s’agirait-il d’une bombe ? — “could it be a bomb?”, with the conditional and the inversion doing all the raised-eyebrow work. Followed by an infinitive it means “what’s needed is”: il s’agit de ne pas se tromper, “the thing is not to get it wrong.”