An Astable Multivibrator is an electronic circuit that continuously switches between its two unstable states, producing a square wave output. It consists of two active components, typically transistors or operational amplifiers, and a combination of resistors and capacitors. This configuration allows it to generate a periodic signal without requiring any external triggering. The output frequency of an astable multivibrator can be adjusted by changing the values of the resistors and capacitors in the circuit. It is commonly used in applications such as timers, oscillators, and flashing LED lights, making it a fundamental building block in electronics.