Nope. If you're on Android, it's a Nostr local relay. See the GitHub link then go to "Releases" to install the APK, or simply install it directly from zap.store ☝️:

GitHub

GitHub - greenart7c3/Citrine: A Nostr relay in your phone

A Nostr relay in your phone. Contribute to greenart7c3/Citrine development by creating an account on GitHub.