Some countries require that foreigners register their stay with the local police. Normally, if you're staying in a hotel then this is taken care of for you. If you are staying at a private residence then you must do the registration.

For example, from [Entry Requirements - Indonesia](https://www.gov.uk/foreign-travel-advice/indonesia/entry-requirements):

> **Registering**
>
> If you stay in private accommodation in Indonesia (not a hotel) you must register your presence with the local police or you could face a fine of Rp 5 million [~ 375 USD]. If you stay in a hotel you will be registered automatically.