STB stands for "Set-Top Box." It is a device that connects to your TV and converts the incoming signal from sources like cable, satellite, or an antenna into a format that can be displayed on your television screen. In the context of a TV antenna, an STB could be used to receive and decode digital broadcast signals if your TV doesn't have a built-in digital tuner or if you want additional features like recording or program guide functionality. It's essentially an intermediary device that enhances your TV's capabilities in terms of signal reception and content presentation.