Mirtilla describes itself as an AI companion, delivered as an app that you download to your device. It is aimed at people who want an AI they can talk to regularly, whether for casual chat or help with day-to-day questions.
The public site shares very little beyond this, so it is worth installing the app and exploring it yourself to see how it behaves. The listing marks it as a paid product, so check the in-app pricing before relying on it.