Functions in JavaScript are fundamental building blocks that encapsulate tasks and can be invoked within or outside of the code. They are first-class objects, meaning they can be treated like other objects, referenced, or passed as arguments. Several ways to define functions exist, including function declarations, expressions, arrow functions, and using the Function constructor, each with unique characteristics and use cases. Function declarations allow hoisting, while expressions do not, and arrow functions offer a compact syntax without their own `this` context. The Function constructor, though less efficient, can define functions globally. Additionally, JavaScript includes generator functions, marked by an asterisk, that yield multiple values on request. The choice of function type depends on the specific use case, such as leveraging hoisting or maintaining a particular `this` context. Understanding these different function types aids in tackling JavaScript's nuances, and tools like LogRocket can assist in debugging by providing insights into errors and user interactions.