Territory Management is the structured account management that gives access to accounts based on the specific properties of accounts. It helps us to get rid of painful part of designing different set of sharing rule to extend sharing of opportunity and case in Salesforce. It also extends the forecast capability for different categories of the structured account system.
It also automates the assignment of account to a specific territory in the structured system, based on a specific property of the account.
Prerequisite of Territory Management: It needs Customizable forecast to be enabled and doesn’t support the Collaborative forecast
Advantages of Territory Management:
• “Automated Account Assignment” based on the characteristics of account
• User & Territory-based Sales reports
• Ability to retain the opportunities even transferred to other territory.
Note: Territory Management is available only upon request to Salesforce.com support team.
Let’s take a real time scenario in which the company Universal Products sells products to their customers. Territory Management is being enabled in the Universal Products.
Let’s walk through the territory management configuration in Salesforce for Universal Products. The following screenshot shows the default forecast setting which is applied to the User’s forecast.

The following screenshot shows Default Territory setting which includes default access for Accounts, Opportunities and Cases associated with the account in the territory. It can be accessed via Manage Territories -> Setting.

The following screenshot shows Territory Hierarchy of Universal Products.

The general configuration of the Territory includes Forecast Manager, Parent Territory, List of users working with the territory, and account assignment rules. The account assignment rules inherit from the higher level territory.
The following screenshot shows general territory configuration for the territory which can be accessed through Manage Territories -> Territory Hierarchy.

Now, let’s see how territory management helps the following:
• Forecasting
• Structured Account System
Forecasting in Territory Management Forecasting in territory management makes Universal Products to forecast their revenue & quantity in different ways. It could be either by user or by territory (Forecast Manager)
Scenario 1:
“SalesRep NorthernStates” of Northern States territory doesn’t have any direct reports. Therefore, the forecast information includes revenue & quantity for the opportunities associated to the accounts in the territory Northern States.
Here, revenue & quantity forecast of “SalesRep NorthernStates” are $4000 & 0 respectively and they are shown in the below snapshot.

Scenario 2:
“SalesRep SouthernStates” of southern states territory doesn’t have any direct reports .Therefore, the forecast information includes revenue & quantity for the opportunities associated to the accounts in the southern states territory
“SalesRep SouthernStates” is working with 2 different territories (Northern States & Southern States); so, he or she will be having 2 different forecasts.
• Northern States Forecast
• Southern States Forecast
Here, the revenue & quantity forecast of SalesRep SouthernStates are $4000USD & 0 respectively for the southern states territory, as shown below.

Here, the revenue & quantity forecast of “SalesRep SouthernStates” is $4000 & 0 respectively for northern states territory which is shown in the below snapshot.

Scenario 3:
“VP Sales States” role of States territory includes the forecast information of direct reports. The VP Sales States is the forecast manager of the territory States which is the parent territory of Northern States & Southern States. So, it includes the forecast information of users in Northern Territory & Southern Territory.
Below is the screenshot that contains the consolidated forecast information of all the users in Northern States & Southern States Territory.

Note:
• SalesRep SouthernStates is working for both Northern States & Southern States; so he or she will be having separate forecast for each of them.
• Pencil icon indicates that forecast manager can override the forecast information.
Structured Account System Structured account system automates the accounts assigned to the territories in the Universal Products based on some criteria specified in the account.
States is the parent territory of Northern & Southern Territory and with a rule:
• Billing Country equals US, USA or United States.
The rule is also inherited by its child territories Northern States & Southern States.
The Below screenshot shows Account Assignment Rule defined in SouthernStates , and Assignment Rule inherited from its parent territory States.

The Below Screenshot shows Account Assignment Rule defined in NorthernStates and Assignment Rule inherited from its parent territory States.

Let’s take a scenario as to how the accounts are automatically assigned to territory based on its criteria.
Scenario 1:
Account Name: Test Account USA and Billing Country: USA
The above criteria only applies to the account assignment rule defined in States territory and not to any of the child territories. So the account is assigned only to States Territory.

Scenario 2:
Account Name: Test Account NS and Billing Zip code: 11001 and Billing Country: USA
The above criteria applies to account assignment rule defined in the Northern Territory and also assignment rule inherited from its parent territory.

Scenario 3:
Account Name: Test Account and Billing Zip Code: 627425 and Billing country: India
The above criteria doesn’t apply to account assignment defined in any of the territories. So the account isn’t assigned to any territories.
The below screenshot show the Test account is not assigned to any territory.

Note: Account could be assigned to any territory manually and it could be assigned to more than one territories.
Conclusion:
Territory Management provides a powerful solution for structuring Users, Account and its associated Opportunity, and Cases. Territory Management suites very well for frequently changing and advanced business requirements. It also helps to predict the revenue for organizations either by user or by territory.
Reference:
https://login.salesforce.com/help/pdfs/en/salesforce_territories_implementation_guide.pdf
http://www.salesforce.com/docs/en/cce/tm_decision_guide/tm_decision_guide.pdf
https://login.salesforce.com/help/pdfs/en/salesforce_forecastsetup_cheatsheet.pdf