A "prime massage gun" is not a single product but a marketing term used by various brands, such as beatXP, Green Lion, and Therabody, to describe different models of handheld percussion massage devices. These devices use rapid back-and-forth pressure and vibrations to relieve muscle soreness, aid in recovery, improve blood circulation, and promote relaxation. Key features to look for include various speed and intensity settings, ergonomic design for ease of use, different interchangeable massage heads for targeted treatment, and powerful batteries for longer operation.