A concise guide for full stack developers to master RESTful APIs: outlines REST constraints (client-server, stateless, cacheable, uniform interface, layered, code-on-demand), compares Fetch (native, minimal) with Axios (JSON serialization, interceptors, error handling, cancellation), details best practices (naming, correct verbs, pagination/filtering, caching, errors), shows a TravelPal example, and covers sending JSON or multipart data for scalable UX.