Salesforce | Six Rule types of Salesforce

1. Validation Rules: Applicable for all fields to validate the entered data.
2. Assignment Rules: Applicable for Cases and Leads to assign them to user based on   condition.
3. Autoresponse Rules: Applicable for Cases and Leads. 
4.  Escalation Rules: Applicable for Cases (assigning issues to users, rerouting or  transfering to another user)
5.  Workflows:  Applicable for all objects 
6.  Approval Process: Applicable for all objects.