You sometimes want to create own tenant when you try to use Azure AD authentication or "School or Work Accounts" independently with your organization Azure AD tenant. Especially, you will really want to create it when you will be in charge of some PoC using Microsoft Azure. You can learn how to create your own Azure Active Directory tenant in this post.
Step by step to create new tenant in Azure portal
Input your organization name and domain name, equal "tenant name", and choose your region.
After a few minutes later, you can find your new tenant from upper-right like below.