A fixed wing plane has to balance its efficiency and speed in the sky with its ability to slowly, steadily drop out of the sky to land. A parachute landing removes this need, and allows the plane to increase weight & speed without worrying about a slow landing.
A parachute landing may be a normal activity used at the end of every flight, or it it may be an emergency response to losing wireless inputs, losing FPV/telemetry feedback, or going outside its designated zone (triggered by GPS). More importantly than not harming the plane, the parachute can make nearly certain that the plane cannot harm anyone by falling on them at speed.
Amateur rocketry enthusiasts have created guides and inexpensive vendors for small, suitable parachutes.