What is a Seed?
A seed is basically an algorithm that tells the game where to place attributes such as mountains, valleys, underground caverns, oceans, water and lava falls, and mineable blocks such as coal, gold, silver and diamonds. This algorithm can be a string of characters or a single letter, number or other character. If you don't enter a seed at the start of a new game, Minecraft will use the current time on the internal computer's clock as the seed.
Creating Seeds
You can use any combination of characters to create a seed. This includes numbers and letters, as well as punctuation marks and symbols. Because the algorithm is case-sensitive, a seed named "A" will create a completely different world than a seed named "a." The values of the characters change depending on the other letters and numbers you use, so creating a world with specific attributes isn't possible without extensive knowledge in hex editing. The fun is in experimenting with different character combinations and exploring the resulting worlds.
Entering Seeds
To enter a seed, tap the "Create New" button on the game's main screen. Enter the characters you chose into the "Seed" text box. Tap the ̶0;Create World̶1; button to create your world and start the game.
Seed Examples
Each seed generates drastically different worlds, and many of them can create features that are not normally seen in the game. For example, the seed "rainbowdash" creates a gigantic waterfall, while the "Notch" spawns a huge lavafall. Using the "minecraftisawesome̴3;" seed gives you a large floating island to explore, and "die123" provides you with a water world dotted by many small islands. The seed "0.5.0" creates a world that has 10 iron blocks, two gold blocks and six diamond blocks directly under your feet as soon as the game begins. Even the simple seed "0" generates mountains housing tall waterfalls and extensive caverns.
Finding Existing Seeds
You can find lists of seeds that other players have created on websites such as the Minecraft Pocket Edition forums on Gamefaqs and iFans, or on Minecraft Seed List and Minecraft PE Cheats (see Resources). Developers have also created iPhone apps that provide lists of seeds with descriptions and pictures of the resulting worlds.