Public Groups in Salesforce

 public group is a set of users. It can contain individual users, other groups, the users in a particular role or territory, or the users in a role or territory plus all of the users below that role or territory in the hierarchy.

Navigation===>

Setup---->Administrator---->Manage Users---->Public Group---->New

Step1---->Enter Label and Group name

Step2---->Select Group Members

Step3---->Add to Delegated Group Members 

Step4---->Save.

Members of Public group can be 

• Individual Users
• Users with given Role
• Users with given Role and Subordinates
• Users from another Public Group 

Delegated Administrators Can Manage Public Groups

Now delegated administrators can create public groups, and you can specify public groups in which delegated administrators can add and remove users in specified roles and all subordinate roles. This way, you can delegate public group management tasks while maintaining strict control over which public groups delegated administrators can manage.

Example:

Group Membership
New Group

Group Information

* = Required Information New Public Group

*Label
*Group Name
Grant Access Using Hierarchies
Search:         Public Groups Roles Roles and Subordinates Users   for:  Available Members --None-- Add Remove Selected Members Group: Cleaning Group Group: sree 1 Group: my group Add to Delegated Administration Groups

Available Delegated Groups --None-- Add Remove Selected Delegated Groups --None--

======>>Enter Details of Group Members and Delegate Group Members. =======>>For More Info     https://ap2.salesforce.com/setup/own/groupedit.jsp?retURL= %2Fp%2Fown%2FOrgPublicGroupsPage%2Fd% 3FretURL%3D%252Fui%252Fsetup%252FSetup% 253Fsetupid%253DUsers%26setupid%3DPublic Groups&setupid=PublicGroups