The Spawn is the biome where you originally spawn in when you join the main game. It was added on release.
The Spawn is the starting biome for all players.
The biome is a grassy area with a few trees and a beige brick pillar structure covering most of the biome. There are four spawn points where the player will spawn upon joining the game. In the middle is the "Pedestal of Awesome" where you can obtain Purple Marker, and there are credits and update boards surrounding it.
The stairs lead up to 4 adjacent biomes: the Shop, Forest, Cave and Abandoned City. There is also a glowing white door leading to the Gallery, and a large, blocked wooden door leading to the Underground Town.
There are currently 9 obtainable markers in the Spawn (Including the Gallery).
They game's developers put notices at spawn. Then they wanted to but "could not remove" the notices. Therefore they hid the notices behind a sign at spawn that says "Nothing to see here. :)."
There used to be text in the update billboard that mentioned Herobrine, a reference to one of the most famous Minecraft myths, and by extension the Mojang update logs that mentioned its removal.
If you go to purple marker and talk to him and say "hi" 50 times, Purple Marker will say "you did it :)" and you'll receive a badge titled "Hi"