What's the big orchestra feedback?

Testing, testing, one, two, three. When your band is trying to perform, feedback is an annoying obstacle, but in the grand orchestra of nature,
feedback is not only beneficial, it's what makes everything work. What exactly is feedback? The key element, whether in sound, the environment or social science,
is a phenomenon called mutual causal interaction, where x affects y, y affects x, and so on, creating an ongoing process called a feedback loop.