The ball starts to the right of the target line and then curves to the left to finish to the left of the target.
Checklist
Aim: Your clubface may be too closed
Grip: One of both or your hands may be twisted too far to the right.
Check the V formed by your thumb and forefinger - it should be pointing inside your right shoulder, not outside.
Ball position: The ball may be too far back in the stance
Stance: not usually a problem but may be too wide
Body alignment: shoulders aimed far too far to the right
Posture: not normally a factor
Swing: The backswing is too much on the inside of the target line which means the shoulders turn too much.
This forces you to turn your hands over during the follow through in order to get the clubhead back on line - resulting in the hook.