what is planning profile Group where and how we use it in CRM campaigns

Hi Experts,

Could you explain me what is the purpose of planning profile groups in SAP CRM campaigns. Please don't mix the TPM in the explanation. If i want to assign a planning profile to my campaign what are the steps i need to perform in the system.

Do we need to integrate with other systems, if yes why do we need the integration.

Just give me High level information with simple scenario.

Thanks In advance.

Regards,

Patil.