A house provides a place for citizens to eat, store food and stay warm..
There are two different known types of houses. In the screenshot there are newly built stone houses. They can be placed as an alternative to wooden homes. They use less firewood to stay heated over time, but they take more stone and wood to build compared to a wood house.
While stone makes better homes in the long run, building them uses up the loose rock that is spread over the map more quickly. After the loose stone is gone, more rock can only be attained through trade or more dangerous rock quarries that require a large workforce.
Cost to upgrade from a Wooden House