The "Multi-Site / Multi-Login" feature refers to the ability to have multiple custom domains registered with your Ory Network project. This allows you to add a different custom UI base URL for each of the custom domains registered in the project, providing a high degree of flexibility. Each domain can serve its own set of UI views that have a common path makeup but different base URL. For instance, if you have multiple online storefronts for different types of products, each managed and developed by one company, they can all serve their UI at the same path, but with different base URLs. This setup allows users who create an account in one of these stores to use it to shop in the other stores as well. The UI served changes depending on the store the user visits, allowing for consistency with the established visual identity of each of your brands. This feature is particularly useful if you want to serve different UI views to customers that interact with different parts of your business, while still allowing them to conveniently use one account that's managed by your Ory Network project. You can find more information about this in the [Ory documentation](https://www.ory.sh/docs/kratos/bring-your-own-ui/configure-ory-to-use-your-ui#multiple-custom-domains-setup). Whether you need this feature or not depends on the specific requirements of your project.