That's where health globes -- floating, crimson spheres that rise from the corpses of your defeated foes -- come in. These globes are the core means of regenerating your health in Diablo III, and all other methods of healing support them. When you pick up a health globe, your health (and the health of any allies in your party) is restored by a fixed percentage depending on the type of globe you've grabbed.
Health globes drive Diablo III's tactical combat, making your lightning-fast decisions during battle intellectually engaging and relevant without adding needless complexity. If you're injured and attacking monsters from afar to avoid further damage, but a much-needed health globe drops, what will you do? Will you put your wand away and make a dash for it, even if doing so requires you to brave a gauntlet of Fallen, or will you cautiously hang back and wait for an opening, fighting defensively so that you aren't overwhelmed? If you're fighting a pack of enemies, can you slaughter the weaker ones quickly enough to saturate the battlefield with health globes so that you'll survive more dangerous attacks? Will you take the right risks at the right time?