Four Thirds is a digital camera system that was developed by Olympus and Panasonic in the early 2000s. It features a sensor size of 4/3 inches, which is smaller than traditional 35mm film but larger than many compact camera sensors. This system was designed to provide a balance between image quality, camera size, and lens compatibility. The Four Thirds standard allows for interchangeable lenses and a variety of camera bodies, making it versatile for different photography styles. It also supports features like image stabilization and advanced autofocus, appealing to both amateur and professional photographers.