“#Tenant Of” is just a note I’ve gotten used to using to let me know what the parent model is. For example, you might have noticed that “#Tenant Of” is only above the belongs_to association for the Account model. This is because all other models are tenants of the Account model. This is all based on building a multi-tenant app where say you can have multiple organizations/businesses where it’s not really the best idea to scope all of the data to the User because the organization/business will need to have multiple Users. Then you have to use something else to scope the data and in this case, it’s a basic Account and everything else is a tenant of that account.