What it measures
Side is the distance, measured at right angles, from the target line to the spot where the ball comes back down to launch level. It is measured in feet, yards or meters.
For a right-handed golfer, a positive value or an R means the ball landed right of the target line, and a negative value or an L means it landed left. Zero means it landed right on the line. Unlike Curve, which is measured from the starting line, Side is measured from the target.
Typical numbers
There is no single average, because Side depends on the target. A more useful measure is dispersion: how widely your shots spread. Strong players often keep most drives within roughly 15 to 25 yards either side of the target line and mid irons within roughly 5 to 10 yards.
Everyday golfers usually see wider spreads, often 25 to 40 yards either side with driver. Side grows with distance, so the same small mistake moves a driver much farther offline than a wedge.
What changes it
Side is roughly the start line plus the curve. Launch direction comes mostly from where the clubface points at impact, with a smaller share from club path. Curve comes mostly from face to path and, with woods, from strike location through gear effect.
Longer shots magnify both parts. One degree of start-line error moves a 270-yard drive almost 5 yards offline, but a 130-yard wedge only a little over 2 yards. Crosswind also changes Side.
What it changes
Side tells you whether the ball found the fairway or green in the air. It is the landing point for bounce and roll, so it feeds directly into Side Total. Across many shots it maps your dispersion, which is what good course strategy is built on.
How to use it
Do not judge a single shot. Look at the spread over ten or more. If most of your shots land on one side, the pattern is consistent and fixable, or you can simply aim for it. If they land on both sides, focus on face control before anything else.
Bay drill: set a fairway-width window on the screen, about 30 yards wide for driver. Hit ten drives and count how many land inside it using Side. Then shift your aim to favor your usual miss and see whether the count goes up. That is a practical way to plan tee shots.