Explain the difference between compile-time polymorphism and runtime polymorphism in Object-Oriented Programming.

Compile-time polymorphism (also known as static polymorphism) occurs when the method to be invoked is determined at compile time based on the method signature. This is achieved through method overloading. Runtime polymorphism (also known as dynamic polymorphism) occurs when the method to be invoked is determined at runtime based on the actual type of the object. This is achieved through method overriding.