Function objects, also known as "functors," are objects in programming that can be called as if they were functions. They typically overload the function call operator, allowing them to be invoked with parentheses. This feature is common in languages like C++ and Python, where function objects can encapsulate behavior and maintain state, making them versatile for various tasks. In addition to their callable nature, function objects can store data and provide additional functionality. They are often used in scenarios like sorting or filtering collections, where they can define custom comparison or selection criteria. This flexibility enhances code reusability and clarity in programming.