What is encapsulation and why is it important?

Encapsulation bundles data (attributes) and methods that operate on that data within a single unit (class), restricting direct access to internal state. Implementation: private fields with public getter/setter methods. Benefits: data hiding (implementation can change without affecting users), validation (setters can validate input), controlled access, reduced coupling. Example: BankAccount with private balance, public deposit() and withdraw() methods that validate amounts. Encapsulation is foundation for maintaining invariants and building robust systems.