The OscillatorNode is a part of the Web Audio API, which allows developers to create and manipulate sound in web applications. It generates periodic waveforms, such as sine, square, triangle, and sawtooth waves, making it useful for creating musical tones and sound effects. Developers can control various properties of the OscillatorNode, including its frequency and amplitude, to shape the sound produced. It can be connected to other audio nodes, such as GainNode or AnalyserNode, to further process or analyze the audio output, enabling a wide range of audio applications.