BUT what is the difference between low intensity cardio and high intensity cardio? what activity would be considered low intensity? etc?

Low intensity cardio would be cardio at say a Level 5 (to paraphrase Body For Life) exertion effort (walking maybe; a step above sitting down). High intensity would be considered a Level 10 (full exertion). It's not which activity would be considered intensive, but rather it's how much physical exertion you perform while doing the activity. You could say going on the Treadmill at 3 miles per hour would be low intensity to one person, while it would be incredibly intense for someone else.

Intensity is a subjective term; any exercise can be at very low intensity. It's all in how much physical exertion you put into it.

thanks!