HTTP Basics

HTTP Header: A list of name and value pairs that contain information that a client and server send back and forth to each other.
Request Header: The information a client (a browser) sends to a server to request a file or resource.
Response Header: The information that the server sends back to the browser.
Resource: The file or information that the browser is requesting.
Request Endpoint (URL): The "location" or path of a resource on the server.
HTTP Method: An action that represents what the client would like the server to do with a resource. Common methods: GET, POST, PUT and DELETE.

Request/Response Cycle

The Request/Response Cycle is the basis for all communication between a browser and a server.

The browser sends a Request to the server for a file (such as index.html or an action (such as submit a form).
The Request is magically routed to the server using many Internet protocols, such as DNS (domain names -> IP addresses) and HTTP.
The server receives the request and decides what to do based on the:
- Endpoint URL - The "location" of a resource (a file or information) on the server.
- HTTP Method - The action that is requested, based on CRUD operations:
  - Create a resource: GET Request
  - Read a resource: POST Request
  - Update a resource: UPDATE Request
  - Delete a resource: DELETE Request
The server performs the requested action based on how we've coded our application.
The server sends a Response back to the client including a:
- File - either static (index.html) or dynamically generated JSON (customers.json).
- Response code - usually either:
  - 200 OK - Success!
  - 404 Not Found - We've all seen these.
  - 500 Internal Server Error - Usually caused by a problem with our code.