A more thorough explanation:

Age discrimination occurs when an employer, labor organization, or employment agency treats an employee unfairly because of their age, if the employee is at least 40 years old. This is protected by the Age Discrimination Employment Act of 1967 (AEDA) and other state regulations.

For example, if an employer decides not to hire someone because they are over 40, that would be age discrimination. Similarly, if an employer lays off older workers while keeping younger ones with the same job performance, that would also be age discrimination.

The key factor in determining age discrimination is whether the employer's decision was motivated by discriminatory intent. It is not enough for the employer to have a good reason for their decision; if age was a factor in that decision, it could still be considered discriminatory.