Health

The health gauge and monitor in Minecraft is based on a single row of 10 heart icons. Each full heart contains two halves, one hit point each (full health is 20 hit points).

Creative mode
In Creative mode the player still has health, but it is hidden from the interface, and the player is invulnerable to everything except falling into the Void or the /kill command.

Hearts
Hearts make up the health meter for the player and mobs in the Survival modes. Each heart represents two hit points, for a total of 20 hit points. Hit points are lost in multiples of one point (i.e. half heart).

Hit points can be lost by: starving; taking fall damage; being attacked by a hostile Mob (or another player if PvP is on); being shot with an arrow; being on fire; touching lava, fire, or a cactus; drowning underwater; suffocating inside a block; falling into the void; being affected by negative potions, or getting caught in an explosion. When the health meter shows two or less hearts (20% or less health), it will begin to shake violently, warning that the player's demise is imminent if health is not restored.

On Peaceful difficulty, the health meter will refill over time. As of 1.8, health is not restored by consuming food, but rather slowly regenerates when the player's Food Bar is at or above, and regenerates fairly quickly for 4 seconds after eating a Golden Apple or 45 seconds with a potion of regeneration.

Damage is split between the health and Armor bars. Each full armor point takes 8% of damage, to a maximum of 80%, rounded up.

On Hardcore mode, hearts have a different texture

Armor


Armor is a craftable item that can be worn in Minecraft's survival mode and survival mode multiplayer that reduces damage to the player while also decreasing the armor's durability. Armor can currently be crafted out of Diamond, Iron, Gold, fire and Leather.


 * Zombies and Skeletons would occasionally wear armor in Survival Test. This armor, however, did not alter any of their stats, and was purely superficial. In 1.4, Zombies and Skeletons can wear armor when spawning, and can pick up armor off of the ground when the player dies, or drops armor.
 * Chain Armor is also craftable, but only by using fire blocks, which cannot be obtained without inventory editing or mods. In survival mode it can be obtained by Trading with a Villager or by killing a skeleton or zombie wearing Chain Armor that is capable of dropping it.

Death


Death occurs when all of a player's hit points are depleted. A "You died!" screen will appear with the player's score displayed (before Beta 1.9pre2, it had &e0 as the score), and the player has the option to respawn at the spawn point (either the last bed the player slept in, their default spawn point, or a spawn point created by commands) or return to the title Menu. In Hardcore Mode, the player cannot respawn and the world will be deleted. Any items and/or blocks that were in the player's inventory are dropped from their head and scattered around the spot where the player died. If they come in contact with dangerous blocks - like lava, fire or cactus blocks - they will be destroyed. Otherwise, according to Notch, "they decay after five minutes, except if the chunk is unloaded, in which case they last forever". The player will also lose any experience accumulated reverting the level back to 0.

Mobs fall sideways to the ground when killed, as shown in the image. If lightning kills them, the lightning charge will stay until the mob disappears.

History
In Indev before suffocation was implemented, players that were covered by blocks could see through dirt and stone. Suffocation was added after Notch discovered that players were abusing this exploit to find underground caves and hollowed carvings. The patch added suffocation damage and making the player unable to see anything when experiencing it. However, this glitch is not completely fixed and is still possible to be done even in the existing version of the game.

Earlier in Survival mode, eating a Red Mushroom would deal the player of damage because they were poisonous.

Trivia

 * A bucket of lava is arguably the most effective weapon in the game, as it doesn't use up durability, does very fast damage, and slows enemies in their tracks. The only downside is that most of the time the mob's dropped loot will disintegrate in the lava. It may also cause nearby trees or wooden buildings to catch fire, possibly even starting vast fires, also it may backfire if the user is hit by the lava and is messy to clear up after use.
 * Transparent blocks will not cause suffocation. As a result, placing a slab above a minecart track can be used to make a barrier through which carts can be ridden without allowing mobs (other than 1 block high Chickens, Pigs, tiny Slimes, Silverfish, Cave Spiders, Bats and Wolves) to wander in.
 * Using a trapdoor functions similarly, in addition to being able to open the door to pass through on foot.
 * Players deal Critical hits when falling (losing altitude).
 * When you die and while you are dead your skin reverts to the default skin. This can be seen by falling from a great height or burning in lava, and checking your inventory moments before death.
 * When falling, the players terminal velocity (the fastest speed one can fall at) is theoretically 78.4 m/s (282 km/h), but in fact there isn't enough height to reach that velocity -- falling from layer 256 to bedrock, they only have time to reach 70 m/s (253 km/h).
 * As of 1.5, mobs give different death messages. There is the standard message, like "Player was shot by Skeleton", a message for when the player dies of fall damage, if the fall damage was a direct result of the mobs attack; "Player was blown from a high place by Creeper" or "Player was knocked from a high place by (Mob Other Than Creeper)". If the player takes the mobs normal form of damage and fall damage within a few seconds of death, the message is "Player was (knocked) from a high place and got finished off by Mob". (Tested in 13w02b).