Apple

Red Apples are food items which fill.

Obtaining Red Apples
As of Minecraft 1.1, there are three sources of Red Apples:
 * They may be found in chests in strongholds or NPC villages.
 * Killing Notch in multiplayer will drop a Red Apple in addition to his inventory.
 * Oak Leaves have 0.5% chance of dropping a Red Apple. (In 1.1.0 they are much easier to find)
 * It seems that oak leaves have a greatly increased chance of dropping an apple when destroyed by a creeper explosion.

As a crafting ingredient
A Red Apple can be used to craft a Golden Apple.

Pros

 * Red Apples can be used as a crafting ingredient to make golden apples
 * Apples are a renewable resource and can be harvested alongside wood.

Cons

 * Red Apples restore only two hunger.
 * Golden Apples are outclassed by Potions of Regeneration, which can be made in groups of three. A golden apple, however, still restores 2 hunger points.

History
Red Apples were added to the game in early Indev. When Indev was still new, Apples were items brought in to replace Brown Mushrooms to heal health. The player would spawn in an Indev House by a chest containing 99 Apples and other tools. In later updates, the chests inside the House were removed, and Apples became impossible to find in a map.

Apples remained impossible to find (without inventory editing or server /give) until Survival Multiplayer, in which one could be obtained by killing Notch. In addition to his inventory, Notch would drop a Red Apple.

In Beta 1.8, apples were made available in the chests in strongholds.

In post-1.0.0 weekly build 11w48a, Oak Leaves have a 1/200 chance of dropping a Red Apple when destroyed. This means Red apples, and thus golden apples, are renewable resources

Gallery
Roter Apfel Pomme rouge Alma Rode appel Jabłko (czerwone) Красное яблоко Red Apple/ch