What is functional programming?

Like OOP (Object-Oriented Programming), FP is a kind of programming paradigm.

It is a programming style in which we write programs in terms of pure functions and immutable data. It treats its programs as function evaluation.

As we use pure functions and immutable data to write our applications, we will get lots of benefits for free. For instance, with immutable data, we do not need to worry about shared-mutable states, side effects, and thread-safety.

It follows a Declarative programming style, which means programming is done in terms of expressions, not statements.

For instance, in OOP or imperative programming paradigms, we use statements to write programs where FP uses everything as expressions.