What does this (Minecraft) mean?

What does this (Minecraft) mean?

That the servers are currently offline for maintenance (repair)

This means that you can't log in until the login server is running.

You can't join the server at the moment because it is offline

The server is being serviced. Try again in 1-5 hours or 2 days

Thanks first of all. But what I ask myself is why a colleague tells me he'll figure it out

It could also simply mean that something isn't working quite well with your internet… Otherwise, the rest of the answers say it all.