A 3.5mm audio splitter is a small device that allows you to connect multiple audio devices to a single audio source. Typically, it has one male 3.5mm jack that plugs into a device like a smartphone or laptop, and two or more female jacks for connecting headphones or speakers. This is useful for sharing music or audio with friends without needing multiple devices. These splitters are commonly used in various settings, such as at home, in cars, or during travel. They are compatible with most devices that have a 3.5mm audio port, making them versatile for listening to audio together.