Angle of Attack (AoA)
Whether the club is moving up, down, or level at the moment it strikes the ball.
A driver wants a slightly ascending angle of attack; irons generally want a slightly descending one to compress the ball and take a divot after it.
More swing mechanics terms
Address
The setup position a golfer takes before starting the swing.
Takeaway
The first foot or two of the backswing, as the club first moves away from the ball.
Backswing
The motion from address to the top, where the club is loaded before the downswing.
Top of the Backswing
The highest, furthest point of the backswing, right before the downswing begins.
Transition
The change of direction from backswing to downswing.
Downswing
The motion from the top of the backswing down through impact.