Referential Transparency is a property of expressions in programming where an expression can be replaced with its corresponding value without changing the program's behavior. This means that if you have a function that always produces the same output for the same input, you can substitute that function call with its result anywhere in the code. This concept is crucial in functional programming languages like Haskell, as it allows for easier reasoning about code and enables optimizations like memoization. When code is referentially transparent, it enhances readability and maintainability, making it simpler to understand how different parts of the program interact.