It's just an app.
An app only available for iOS and still open via invite (though they're not hard to come by). Not exactly a wide-open platform.
Even so, I'm impressed how fast communities are forming on the nascent "social audio" platform. Twitter and Facebook are developing competing features, so we'll see if Clubhouse can retain something distinctive.
The Hawaii Club on Clubhouse now has 2,500 members, and a full calendar of diverse conversations: https://www.hawaiiclubhouse.org