/seed /seed | Difficulty: Trivial Usage: /seed
This command is used to display the seed of your current world. It will display in your chat.
What is a seed?
A seed is "the code" of your world. It's a unique number. This number is used to create a clone of another world (create world --> world options --> text space for seed --> insert number). It will create the excact default form of the world.
However, this cloned world will NOT have the excact same mobs or changes caused by a player. Also, the player spawnpoint can be changed.
For more info, go to the minecraft Wiki.