What is Middleware protection in Laravel, and what role does it play in a real application?

What is Middleware protection in Laravel, and what role does it play in a real application? In Laravel, middleware protection should be understood as part of a larger application architecture rather than as an isolated API call. Protected routes can require the appropriate Sanctum authentication middleware. 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: Laravel Sanctum supports lightweight API token authentication and first-party SPA authentication patterns without requiring a full OAuth server for every use case. The specific focus here is middleware protection: Protected routes can require the appropriate Sanctum authentication middleware. 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.