Put prosody. Don't know what to do next?

Question

Domain Name System

Installed the PROSODY server on the VPS for "academic" purposes. Faced with several new entities with which I had no business before:
1. Domain name.
2. Certificates.
3. Interserver communication between JABBER servers.
1. (In general, it is not clear to me why it was impossible to simply use the IP address?) I bought a name, how I could set up addressing. I don't understand why there are so many types of DNS records (A-, TXT-, CNAME-, etc.). Suggest a tutorial for beginners, telling which records are needed for what, when which ones are used.
2. Made a certificate for the domain using Let's Encrypt. For the sake of work, certbot picked up apache, although I didn’t need the site right now.
2.1 Why does PROSODY use certificates at all: does it encrypt any data transfer between the client and the server, or only in the case of BOSH - XMPP over HTTP?
2.2 Is it possible to obtain/renew certificates without an HTTP server? It seems that I saw something on the certbot.org website about API support by some VPS providers (about a dozen). But maybe there are other options?
3.S2S. In general, it is difficult to imagine how this happens from the point of view of the client. Should my server be able to search for contacts on other servers? How can the [email protected] account write to the [email protected] contact?
And in general I do not have enough information. The site prosody.im only instructions on how to enable this option. What is she for? What gives? How to use?
Same group chats. To communicate with more than 2 accounts in one chat, do you need to enable muc-module or not?
Thanks in advance for any help.

Answer 1

Don't know what to do next?

Read. Read a lot.
Read about DNS. Read about X.509 (Hint: you can issue a certificate without LE. LE is needed in order for the certificate to be issued by some, but generally recognized world CA).