A 9V battery is a common type of battery that provides a voltage of 9 volts. It is often used in various electronic devices, such as smoke detectors, remote controls, and guitar pedals. The battery typically has a rectangular shape with two terminals, making it easy to connect to devices. These batteries come in different chemistries, including alkaline, lithium, and rechargeable nickel-metal hydride (NiMH). The choice of battery type can affect the performance and lifespan of the device it powers. Overall, the 9V battery is a versatile power source for many household and electronic applications.