In the world of The Side Ways, there are Seven Domains, each defined by how their Reckoners perceive the world. The Domains are:
You can find out more about each of the Domains in additional "Lore" posts.
In Awake, Kendra learns the Song of the Houses from Vannia:
Earth, the Mother, first and last, Bearing Blood, the eldest sign. Chaos leaves the patterned path, Draws out Sight to spy and find. Flux pulls power from the round. Increase seeks the gain of gain. Release opposes any bounds. Ever balanced, poised Domains. Each and every, all and one. Seven equal, seven done.
This is a mnemonic that young Reckoners use as a reminder of lessons about the history of the Domains in the world. It is also sometimes a trigger for a Way of Remembrance which provides more details about each House.
The terms "Domain" and "House" are often used more-or-less interchangeably. They aren't exactly the same, though.
One's Domain encompasses everything about how one experiences the world. It is one's fellow Reckoners, their Ways, places, creatures, ideas and ideals. The House affiliated with each Domain is, essentially, all the Reckoners who choose to engage in any level of administration or governance of a Domain. So one might be a Reckoner of Chaos, but choose to be alone and disconnected from the various politics and machinations of the House. It's a slight distinction, and mostly important to those who are on both ends of the curve; active leaders and those actively uninvolved.