APIs act as communication bridges between software systems, enabling data exchange and functionality reuse. Flask, a popular Python microframework, simplifies RESTful API development by mapping URLs and HTTP methods to Python functions. Developers create a Flask instance, then use decorators like `@app.route()` to define endpoints that handle client requests and return responses, often in JSON format.

Building an API involves defining routes for different HTTP verbs: GET for data retrieval, POST for creating resources, PUT for full updates, PATCH for partial updates, and DELETE for removal. Flask's `Flask-RESTful` extension streamlines this by grouping related behaviors into resource classes, automatically handling method mapping and reducing boilerplate code for complex endpoints.

For example, a `Mangas` resource class can define `get()` and `post()` methods. Flask-RESTful manages the routing, while `make_response()` gives developers explicit control over HTTP status codes like 201 Created. This approach contrasts with plain Flask's `jsonify()`, which automatically converts responses to JSON but offers less granular status control, a key consideration for robust API design.