Whether an activity is low, moderate, or vigorous-intensity varies according to your personal fitness level. As a general guideline, though:
For most people, aiming for moderate-intensity exercise is sufficient to improve your overall health. You should breathe a little heavier than normal, but not be out of breath. Your body should feel warmer as you move, but not overheated or sweating profusely. While everyone is different, don’t assume that training for a marathon is better than training for a 5K or 10K. There’s no need to overdo it.