IRC is awesome to talk with other oddballs as you and me.
I first tried it not long ago, and as a completely uninitiated person would do, looked for guides.
But, no surprise here, all looked more or less the same and didn't cover the most basic questions such a person should have. So here is my go at it.
This, however assumes that you have read one of those basic guides, so you know what is a channel, a network, a nick, nickserv (for registered nicks) etc.
You choose a client (e.g. Hexchat). They all more or less accomplish the same. Granted is that a user of client A can talk to user of client B.
The messages you receive and send are not logged by the server, which is just a pipe without memory.
Clients usually do log them, but that's all. Your log will exist in your storage device; if it's gone, so are your messages, you can't retrieve them.
This also means that if you are in a channel and lose connection for 10 min, you cannot tell if someone sent messages in the meantime (well, not without asking the other participants), much less what they said.
There are some channel owners that do log all messages and keep them availabe, e.g., Ubuntu channels. This is not the norm, though.
In the most bare IRC network, there is no way to message a disconnected person.
However, some networks such as Libera Chat, the most popular one, have a MemoServ command, allowing users to send short messages to disconnected but registered users.
Yes, this is simple communication. Text only.
Hexchat actually has a /send command to send files. However,
this only seems to work between two Hexchat users.
It's just an obscure way to communicate, but by no means safe as in anonymity; Quite the contrary. Plain text is used. No encryption. Assume all text you send there is visible to the whole freaking world. Crazy!
To be continued