Add Hypertext transfer protocol (HTTP) section

Author: donnemartin

README.md

@@ -1451,3 +1451,24 @@ If queues start to grow significantly, the queue size can become larger than mem
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   <i><a href=http://www.escotal.com/osilayer.html>Source: OSI 7 layer model</a></i>
 </p>
+
+### Hypertext transfer protocol (HTTP)
+
+HTTP is a method for encoding and transporting data between a client and a server.  It is a request/response protocol: clients issue requests and servers issue responses with relevant content and completion status info about the request.  HTTP is self-contained, allowing requests and responses to flow through many intermediate routers and servers that perform load balancing, caching, encryption, and compression.
+
+A basic HTTP request consists of a verb (method) and a resource (endpoint).  Below are common HTTP verbs:
+
+| Verb | Description | Idempotent* | Safe | Cacheable |
+|---|---|---|---|---|
+| GET | Reads a resource | Yes | Yes | Yes |
+| POST | Creates a resource or trigger a process that handles data | No | No | Yes if response contains freshness info |
+| PUT | Creates or replace a resource | Yes | No | No |
+| PATCH | Partially updates a resource | No | No | Yes if response contains freshness info |
+| DELETE | Deletes a resource | Yes | No | No |
+
+*Can be called many times without different outcomes.
+
+HTTP is an application layer protocol relying on lower-level protocols such as **TCP** and **UDP**.
+
+* [HTTP](https://www.nginx.com/resources/glossary/http/)
+* [README](https://www.quora.com/What-is-the-difference-between-HTTP-protocol-and-TCP-protocol)