Dont know what app you installed, but there are a whole bunch of them; some are indeed similar to X, or 'micro blogging' as it is refered to in general. Others focus more on long-form content like articles (one such app is called yakihonne), or pictured similar to instagram (olas for example). There are cooking recipe apps, chat apps, audio/video chat room apps...

The same protocol and its socialgraph can be leveraged to build an appstore (zapstore for example), wiki's.

And you can use the same profile you use now in all of them, carrying your socialgraph (the people that follow you, and the people you follow) with you.

Welcome to the Nostr rabbithole

Nostr works like a protocol