FusionAuth is a single-tenant solution that supports multiple tenants within a single instance. This allows clients to create separate namespaces for their clients, enabling each client to manage their users, permissions, and user details discretely. Tenants are useful for organizations with multiple environments such as development, staging, and production, where a single instance of FusionAuth can be used to service multiple environments, reducing complexity and infrastructure costs. Additionally, tenants enable the creation of separate identities for clients, which is necessary when a platform needs to provide different authentication resources for each client. This feature also allows developers to create their own tenant so they can develop, create, and delete users without affecting the rest of their team.