Hi Satyakam,
Sharing rules can be based on who owns the record or on the values of fields in the record. For example, use sharing rules to extend sharing access to users in public groups or roles. As with role hierarchies, sharing rules can never be stricter than your org-wide default settings. They just allow greater access for particular users.
Each sharing rule has three components.Share which records?
You can share records owned by certain users or meeting certain criteria. Criteria-based sharing rules determine what records to share based on field values other than ownership.
With which users?
You can define groups of users by role or by defining a public group. A public group is an admin-defined grouping of users that can be used to simplify the creation of sharing rules. Each public group can be a combination of:individual users
roles
roles and subordinates
other public groups
What kind of access?
You can assign either Read-Only or Read/Write access.
Sharing rules work best when they're defined for a particular group of users that you can determine or predict in advance, rather than a set of users that frequently changes. For example, in the Recruiting app, it’s important to share every position, candidate, job application, and review with every recruiter. Since recruiters all belong to either the Recruiting Manager or Recruiter roles in the role hierarchy, we can easily use a sharing rule to share those objects with the Recruiting Manager role and its subordinates.
Alternatively, consider another use case from the Recruiting app: interviewers need read access on the candidates and job applications for people they're interviewing. In this case, the set of interviewers is a lot harder to predict in advance—hiring managers might use different sets of interviewers depending on the position for which they're hiring, and the interviewers might come from different groups in the role hierarchy. So, this use case probably shouldn't be handled with sharing rules—the team of interviewers for any given manager is just too hard to predict.
Thanks