Global extrema refer to the highest and lowest values of a function over its entire domain. The highest point is called the global maximum, while the lowest point is the global minimum. These points are important in various fields, including mathematics, economics, and engineering, as they help identify optimal solutions. To find global extrema, one often uses calculus techniques, such as taking the derivative of a function and setting it to zero to locate critical points. Additionally, evaluating the function at the boundaries of the domain is essential, as global extrema can occur at these endpoints as well.