Inappropriate sinus tachycardia (IST) is a condition in which an individual's resting heart rate is abnormally high (greater than 100 beats per minute), their heart rate increases rapidly with minimal exertion, and their rapid heart rate is accompanied by symptoms of palpitations, fatigue, and exercise intolerance.
Sinus tachycardia is a normal heart rhythm accelerated to 100 beats or more per minute. In it's most benign for, it is a natural response to physical and emotional stress. If you run a good distance and stop, or experience a significant fright, the rapid heart beat you feel is most likely sinus tachycardia. In these forms, sinus tachycardia is perfectly normal and by itself does not require medical attention.
IMHO, I would say these two types of sinus tachycardia are not the same for differential purposes. Please remember I am not a Dr. so do check with your's if you are having concerns.