Service medal

A service medal is an award to personnel who participated in designated wars, campaigns, or expeditions, or who have fulfilled specific service requirements in a creditable manner.

Campaign medal
Campaign medals are similar to service medals (and are sometimes even referred to as service medals), however the main difference is that a campaign medal is awarded to a military member who participates in a military operation whereas a service medal is blanket awarded to everyone in the military regardless of campaign credit.

USA
Two current examples of a service medal currently issued by the United States Armed Forces are the National Defense Service Medal and the Global War on Terrorism Service Medal. The National Defense Service Medal is issued to a service member upon joining the military usually after completion of basic training. The Global War on Terrorism Service Medal is presently issued to any active duty member of the United States military after ninety days of service.