The HTC Vive Tracker (99HANL008-00) makes your VR gaming more realistic by enabling you to turn real-world objects into VR accessories and use them in your game,  allowing you to expand your VR gaming arsenal and add more realism to your gaming experience.  Aside from sensors that get picked up by your HTC Vive or Vive Pro's base stations, the HTC Vive Tracker comes with a built-in tripod adaptor, a Pogo pin, and a USB port.

The HTC Vive Tracker enables VR gamers to bring in any real-world object to their VR world and use them as an accessory, allowing them to have more realistic and immersive experiences compared to just using HTCs Vive controllers. 

Read more about HTC Vive Tracker on the official Vive website