An HDMI splitter is a device that allows you to connect one HDMI source, like a Blu-ray player or gaming console, to multiple displays, such as TVs or monitors. It takes the single video and audio signal from the source and duplicates it, sending the same content to each connected display simultaneously. These splitters are useful for situations where you want to show the same content on different screens, like in a home theater setup or during presentations. They come in various configurations, supporting different resolutions and features, ensuring compatibility with most HDMI devices.