What is Dependency injection in Laravel, and what role does it play in a real application?

What is Dependency injection in Laravel, and what role does it play in a real application? In Laravel, dependency injection should be understood as part of a larger application architecture rather than as an isolated API call. Controllers can receive services and framework dependencies through constructor or method injection. A strong understanding includes its purpose, the layer where it belongs, the data or request flow it affects, and the situations where another mechanism may be more appropriate. Practical context: Controllers group related request-handling logic and commonly coordinate validation, services, models, redirects, views and API responses. The specific focus here is dependency injection: Controllers can receive services and framework dependencies through constructor or method injection. This question is designed to test not only terminology, but also how the concept fits into Laravel's request, application, database, security, or deployment workflow.