Could u please explain me about sites in Manage Engine Service Desk Plus - MSP editon???

Does sites means a custom portal in which users accounts are added ? 

Really confused please help me out ????

And please guide me how to customize  portal for different users like .. ADMIN \ Customers\Helpdesk Staff\Product Support Team ???

One more thing , How edit the labels inside the portal ? If you give me the steps in details would be much appreciated :)

I am getting very good response from your support team .... I hope the support and response from you guys would be the same until the end !!! :)