What is the need for Territory Management in Salesforce?

Hello Prachi,
Territory Management is a tool that provides specific and flexible security control for accounts and children of accounts. Security control for Territory Management can be based on any field within accounts. With the Veeva CRM application you will likely use Territory Management to control security to your accounts and use the Role Hierarchy to control security to other objects.Particularly if your organization has a private sharing model, you may need to grant users access to accounts based on criteria such as postal code, industry, revenue, or a custom field that is relevant to your business. You may also need to generate forecasts for these diverse categories of accounts. Territory management solves these business needs and provides a powerful solution for structuring your users, accounts, and their associated contacts, opportunities, and cases.

Salesforce Handles Territory Management allows you to manage the roll-up of information among your company's territories. The hierarchy structure is not based on traditional titles, but rather on a hierarchy of roles. Multiple people with different titles can be assigned to the same role. Users always have access to the data that is owned by or shared with users assigned to roles below them in the hierarchy. A user’s role also determines which data is accessible to him or her in forecasts.
You can refer the following link for more information:
https://help.salesforce.com/articleView?id=faq_getstart_how_does_salesforce.htm&type=5
Thanks.