Cardio endurance training is one component of the Fitness Triad (strength, athleticism, endurance) or, as we usually divide it, strength, calisthenics, and cardio.
Unless one is a competitive runner, swimmer, biker, or rower, we believe it's good to mix up cardio exercises because just doing one improves one's efficiency too much for the cardiac stress you are looking for.
Cardio training (ie exercising your heart muscle) is like anything other muscle: you want to stress it without injuring it. That can either mean keeping your heart rate at 55-85% of your max heart rate for 30 minutes (depending on age), or it can mean HIIT cardio training with sprints. I recommend the latter for time efficiency and because it is gentler on your body.
I no longer recommend road-running, especially distance road running. A morning 5-mile jog is harmless but the main benefit is mental because few joggers get their heart rates very high. Distance runners/races (ie from marathoners to 50 milers to 100-milers) are admirable in their dedication and amazing endurance but it just isn't healthy for joints, heart, body inflammation, risk of kidney damage, and so forth. Pheidippides, who was a professional distance courier (before cell phones), died in Sparta.
Our current "Maggie's Recommended" general fitness training for the cardio component is roughly one hour of endurance cardio (a mix of elliptical, treadmill, stairmaster) keeping a solid (ie 55+% but sub-max heart rate; and 1/2 hour of HIIT cardio (30-60 second max sprints on rower, treadmill, combat bike, stairmaster, etc) with triple slow recovery times; and the mix of cardio and athleticism training in calisthenics/exercise classes.
I almost forgot to mention sports. Two hours of basketball is excellent cardio/athleticism exercise. Same for martial arts, or a tennis class.
Remember, unless you are in training for multiple hours daily, you can not lose weight by doing cardio exercise.
