MIME-Version: Defines the MIME version (current: 1.1).
Content-Type: Defines the type of data in the message body (e.g., image/jpeg, text/html, video/mp4).
Content-Transfer-Encoding: Defines how messages are encoded into 0s and 1s for transport.
- Encoding types: 7-bit, 8-bit, Binary, Base64, Quoted-printable.
Content-ID: Uniquely identifies the message in a multiple message environment.
Content-Description: Defines whether the body is image, audio, or video.

Distributed client-server service, a system of interlinked hypertext documents and resources.
Invented by Tim Berners-Lee in 1989.
Uses URLs and HTTP to connect users to websites via web browsers.
Web pages are distributed globally and linked together.

Hypertext: System of links connecting documents, allowing navigation between web pages.
Web Browser: Software applications (Chrome, Firefox, Safari) used to access and view websites.
Uniform Resource Locator (URL): Unique address for each web resource.
- Structure: PROTOCOL://HOST:PORT/PATH
- Example: https://www.google.com/search?q=cheatsheet

Static Documents: Pre-written HTML documents stored on a server, delivered as-is to the client.
Dynamic Documents: Generated by server-side scripts (e.g., PHP, Python, Node.js) in response to client requests.
Active Documents: Contain client-side scripts (e.g., JavaScript, applets) that run on the client's browser.

Protocol enabling communication between web servers and clients.
Web server uses port 80, web client uses a temporary port.
Uses TCP services.
Supports multiple request/reply exchanges over a single TCP connection.
Prior to HTTP/1.1, used non-persistent connections; persistent connections are default in HTTP/1.1 and later.
Latest version: HTTP/3 (released 2022), uses QUIC (Quick UDP Internet Connection) to reduce latency and improve speed.

Request Message (Client to Server):
- Request Line: METHOD URL VERSION (e.g., GET /index.html HTTP/1.1)
- Header Lines: Key-value pairs providing additional info (e.g., Host: example.com, User-Agent, Accept).
- Body: Optional, contains data for methods like POST (e.g., form data).
Response Message (Server to Client):
- Status Line: VERSION STATUS_CODE PHRASE (e.g., HTTP/1.1 200 OK)
- Header Lines: Key-value pairs (e.g., Content-Type: text/html, Content-Length).
- Body: Contains the requested resource (e.g., HTML content, image data).

Method	Action
GET	Requests a document from the server.
HEAD	Requests information about a document but not the document itself.