Difference between Sales Cloud and Service Cloud

Kindly check the below link for Sub modules of CRM
http://www.infallibletechie.com/2013/05/sub-modules-of-crm.html

Sales Cloud:
Sales Cloud refers to Sales module in CRM. Sales module include Lead Conversion, Account Management, Opportunity Management, etc.

Service Cloud:
Service Cloud refers to Service module in CRM. Service module includes Case Management, etc.
To know more about Service Cloud, check the following link: