Forward-slip Vs. Sideslip
Two forms are employed, the forward-slip and the sideslip. Aerodynamically these are identical once established, but they are entered in different manners and will create different ground tracks and headings relative to those prior to entry. Slips are particularly useful in performing a short field landing over an obstacle (such as trees, or power lines), or to avoid an obstacle (such as a single tree on the extended centerline of the runway), and may be practiced as part of emergency landing procedures. These methods are also commonly employed in flying into farmstead or rough country airstrips where approach hazards are present.
Read more about this topic: Sideslip Angle