The goal of multitenancy is to maximize resource sharing by allowing multiple users (tenants) to log in and use a single sever/cluster at the same time, in a tenant-isolated manner. That is, each user is given the experience of using his/her own server, rather than a shared environment. Multitenancy ensures optimal performance of the system's resources such as memory and hardware and also secures each tenant's personal data.
You can register tenant domains using the Management Console of WSO2 products.