Hi!
I will add an explanation in the next update.
But basically...
Houses increase the number of workers and you can send slaves to live alone in them, it won't change anything but it will allow you to have another slave in your house(although there is no other slave at the moment).
The tavern is to increase the happiness based on the social lvl of the slaves.
The brothel also increases happiness and gives money based on the slave's kinky stats.
The hospital does nothing at the moment but is to cure the slaves when they are sick or when they are pregnant.
The chapel is to recover morale by praying.