This mod is very simple and aims to do one thing: bring Heart Containers from Zelda over to Minecraft. You start the world with 3 hearts, just like in Zelda. And when you pick up a Heart Container item, which you can find randomly inside of loot chests anywhere, you'll increase your max hearts by 1 permanently. The maximum amount of hearts is 20- again, just like in Zelda.
That's it! The mod works in multiplayer as well, of course. Have fun! =)