How does Http and Https proxies work

HTTP proxy gets a plain-text request and [in most but not all cases] sends a different HTTP request to the remote server, then returns information to the client. The specific flow of the HTTP proxy server is as follows.

HTTPS proxy is a relayer, which receives special HTTP request (CONNECT verb) and builds an opaque tunnel to the destination server (which is not necessarily even an HTTPS server). Then the client sends SSL/TLS request to the server and they continue with SSL handshake and then with HTTPS (if requested).

Proxy connection of https communication.