Nambu–Goto action

The Nambu–Goto action is a mathematical formulation used in string theory to describe how a fundamental string moves through space and time. It measures the area of the surface—called the worldsheet—that the string sweeps out as it vibrates and travels. The action acts as a principle that guides the string’s behavior: the string naturally follows the path that minimizes this area, similar to how a soap film spans a wireframe in the smallest possible surface. This concept helps physicists understand the dynamics of strings and their role in the universe's fundamental structure.