IIRC they can't use it for commercial use, and I think that they may not be able to encrypt it. But in theory, they could talk about pretty much anything. Like, it could span everything that you might see on Reddit or something like that. But...when you get a lot of people together whose common factor is that they're all interested in ham radios, they tend to talk about ham radios. :-)

https://meshcore.io/map https://meshmap.net/

If you can make it to a repeater that is in a good spot, there are decent chances you would reach someone. Now, of course, repeaters require someone to set them up and maintain them. If you live in the middle of nowhere or in a country with super strict radio laws (like Belarus or India), you are mostly out of luck. But if you live in a place where it is illegal, chances are that ham radio will not be trouble-free either, to put it mildly.