The PCTV USB2 2821 Capture Windows driver is a driver for the PCTV USB 2.0 device, typically used for TV tuning or video capture. The device is made by PCTV Systems (or later by a company like Hauppauge, depending on the specific model). The PCTV USB 2.0 series includes USB TV tuners and video capture devices that allow you to capture live video from an antenna, cable, satellite, or external video sources, and stream or record the content on a Windows PC.
The driver (PCTV USB2 2821) ensures that Windows can properly recognize and communicate with the hardware device. Without the correct driver, your computer may not be able to interact with the USB capture device, and you might not be able to use it for tasks like watching TV or capturing video.