@Bryce *******
It is a "notification of foreigner in residence" form that you or your land lord or your hotel files to show that a foreigner is staying at a specific address. They have an online and mobile app for it but it is currently down meaning you go file in person.
There are (or were) three possible receipts you could show that a TM30 was filed on you. The paper receipt from filing in person, the screen grab of having done it on the website OR the mobile application