Could someone explain why/how this sample scene kit code works?

I am working with scene kit and am trying to make a first person game. I found this sample code for making the first person camera with a pan gesture. Everything works but I do not understand what is going on here. Could someone explain what is happening?

    func lookGestureRecognized(gesture: UIPanGestureRecognizer) {

    //get translation and convert to rotation
    let translation = gesture.translationInView(self.view)
    let hAngle = acos(Float(translation.x) / 200) - Float(M_PI_2)
    let vAngle = acos(Float(translation.y) / 200) - Float(M_PI_2)

    //rotate hero
    heroNode.physicsBody?.applyTorque(SCNVector4(x: 0, y: 1, z: 0, w: hAngle), impulse: true)

    //tilt camera
    elevation = max(Float(-M_PI_4), min(Float(M_PI_4), elevation + vAngle))
    camNode.rotation = SCNVector4(x: 1, y: 0, z: 0, w: elevation)

    //reset translation
    gesture.setTranslation(CGPointZero, inView: self.view)
}