What is the difference between a regular fast heartbeat and a fast heartbeat post workout? i have been wondering why pumping the heart during a workout is good to do but not necessarily a fast heartbeat without a workout. is there a difference?

Rapid heart beat during a workout is the response of the body to demands for a higher cardiac output to meet the demands. This is a physiologic phenomenon and is generally beneficial. A fast heart beat without a workout is abnormal and occurs in response to infection, inflammation, as a side effects of drugs and due to ab abnormality of the heart rhythm resulting from heart disease .

It is supply demand, while physiologic activities, physical exercise, even simple emotions can trigger a fast heart rate, some other times pathological processes, such as physical pain, fever or low blood or anemia among many others can trigger a fast heart rate.