It has "toots" not "tweets" - and its mascot is a long-extinct mammal - not a bird.
Those differences are possibly the easiest to understand for social media users leaving an Elon Musk-run Twitter for the suddenly-popular Mastodon platform.
Since the tech billionaire's takeover of Twitter was confirmed, his moves to cut staff and impose an eight US dollar monthly charge for blue tick verification has turned off many users - leaving them seeking alternative microblogging sites.
One that's suddenly taken off in popularity is Mastodon. But where Twitter is a single website with a central news feed, Mastodon is a network of thousands of individual communities - called "instances".
To explain more, Kathryn is joined by Robert Gehl. He's an associate professor in the Department of Communication and Media Studies at York University in Canada and the author of a number of books, including one out this year called Social Engineering: How Crowdmasters, Phreaks, Hackers and Trolls Created a New Form of Manipulative Communication.
Also joining the conversation is is Aurynn Shaw. She is the administrator of the New Zealand-based Mastodon instance, Cloud Island.