Launch angle measures the vertical angle of contact — 0° is horizontal, 90° is straight up. Most extra-base hits come in the 10-25° range.
Below 10° tends to produce ground balls; above 35° leads to flies/pop-ups.
The ideal angle correlates with exit velocity — harder hits expand the productive angle range.
The 'fly-ball revolution' has gradually pushed average LA upward since the 2010s.