Those who have never had military or law enforcement training tend to use the terms interchangeably in error. Here's s good short article by Jim Wilson that breaks it down very simply:
Cover & Concealment
You should always know where available cover and concealment is located in your area.
By Jim Wilson
For the defensive shooter there is a distinct difference between concealment and cover. Concealment is anything that will help you hide, but does not stop bullets. Examples that quickly come to mind are bushes, shrubbery and shadows. An alert citizen, who sees potential trouble while it is still a ways away, might step behind concealment so that he or she is not seen while observing and making a determination about the potential threat....