My friend has cancer of the throat and recently underwent surgery to remove the cancer? Will he need radiation?

Short list. Side effects include decreased saliva production, throat irritation and soreness with some discomfort on swallowing. Possible hoarse voice from vocal cord inflammation. These are from an oncologist's point of view; for more information contact your radiation therapist.
Depends. Location, nodal involvement and adequacy of resection will help to determine if he requires any additional treatment such as radiation therapy.