@Gargron In my conversations, the federated/decentralized part has been pretty easy: “there are lots of servers that can all talk to each other, like email, and you can run your own if you really want” has worked well. “Like email” is the key phrase, I’ve found.

I’ve had a harder time with the basic function/purpose. Preceding the above with “it’s line Twitter, but” works pretty well, but there’s good reason not to want to start off with that comparison.