Bedrock

"Bedrock lives at the bottom of the overworld and the top and bottom of the Nether. It was added on the tenth day of Minecraft's development - 20 May 2009 - only three days after the game was released to the public for the first time. It's older than water, lava, ores and logs. But dirt, grass and stone are older still."

- Duncan Geere

Bedrock is a block that is indestructible in survival.

Natural generation
Bedrock comprises the bottom-most 5 layers of the Overworld in a rough pattern, although the first to fourth layers are predominantly flat bedrock with only rare gaps, rendering the very bottom, completely flat fifth layer (at y=0) mostly inaccessible. In the Nether, bedrock comprises both the top and bottom four layers in a rough pattern. At the top of the Nether, bedrock prevents the player from going past layer 127. It can also be found at the sides of the Nether.$$

In the End, individual bedrock blocks make up the natural end crystal structure, and the bedrock remains after the destruction of the crystal. Bedrock additionally forms as as part of the exit portal that generates at the center of the central End island. It also forms the randomly generating gateway portals that lead back to the obsidian platform.

Post-generation
End gateway portals, the ones which are generated upon killing the ender dragon,mare also composed predominantly of bedrock.

Obtaining
Bedrock is unbreakable in Survival mode, regardless of the tools used. It also cannot be moved by pistons or destroyed by explosions that are present in survival gameplay. Bedrock can be obtained or broken only in Creative mode, by using commands, or by pressing when hovered over a bedrock block in creative mode. Even if theoretically broken in Survival mode, bedrock would not drop as an item.

Usage
Bedrock's primary usage is as a solid unbreakable block. It also prevents mob spawns and is the only solid block that beacon beams can shine through. When placed above a beacon on Legacy Console and PlayStation 4 editions, it turns the beam black.

Additionally, when set on fire, the fire on bedrock never extinguishes naturally, similarly to the fire on netherrack. This varies per dimension.

Block states
In Bedrock Edition, bedrock uses the following block states:

Trivia

 * In the Legacy Console Edition, only the highest layer in the Nether of naturally spawned bedrock is unbreakable.
 * It is possible, but rare, for ore to be found encased in bedrock.
 * Strongholds can cause a bedrock not to form within its bounds.
 * From its addition in Classic through some versions of Alpha, bedrock's texture file was called Rock.png.
 * In Java Edition, the patterns of bedrock are consistent in all worlds regardless of world seed (except Superflat). In Bedrock Edition, the patterns are dependent on the seed in the Overworld, however, they are still consistent in the Nether.
 * The bedrock texture, regardless of the current default resource pack (Programmer Art or Default), is basically the stone block with a really high contrast.