chore(kb): start articles about proxies

knowledge base/proxy.md

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+# Proxy
+
+Application acting as an intermediary between a client requesting a resource and the server providing that resource.<br/>
+It may reside on one's local host or at any point between it and destination servers on the Internet.
+
+Proxy servers passing unmodified requests and responses are usually called _gateways_ or _tunneling proxies_.<br/>
+_Anonymous_ proxies reveal their identity as proxy servers but do not disclose the originating IP address of clients.<br/>
+_Transparent_ proxies identify themself as proxy servers but also give the originating IP address away using HTTP header
+fields like `X-Forwarded-For`.
+
+1. [Forwarding proxy](#forwarding-proxy)
+1. [Reverse proxy](#reverse-proxy)
+1. [Further readings](#further-readings)
+
+## Forwarding proxy
+
+Internet-facing proxies used to retrieve and eventually cache data from a wide range of sources (in most cases, anywhere
+on the Internet).
+
+## Reverse proxy
+
+Proxy servers that accept connections from clients, forward them to one or more backend servers to handle the requests,
+and return the response as if it came directly from them.<br/>
+This should leave the clients with no knowledge of the backend servers.
+
+Reverse proxies commonly perform load-balancing, authentication, decryption and caching.
+
+## Further readings
+
+Reverse proxies:
+
+- [Nginx]
+- [Traefik]
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+[nginx]: nginx.md
+[traefik]: traefik.md
+
+<!-- Files -->
+<!-- Upstream -->
+<!-- Others -->