Minecraft wiki entry for End_survival, associated text: It has only two mobs after the defeating of the ender dragon: endermen and shulkers.
It has a lot of empty space for building.
It is very flat and easy to see across.
It has a large amount of obsidian, and an unlimited amount of ender pearls and an unlimited amount of end stone, with the ability to respawn the ender dragon.
Unlike the Nether, it can have both water and lava in it for cobblestone. The player can also grow trees and crops.
The player can go to the outer islands, where they can find chorus fruits, chorus plants and end city-related things.
The End is the only place where the player can find an end ship, where they can get the elytra, an extremely useful item used for flying. It is also the only source of the invaluable resource of Shulker Shells.
On servers, it is usually the least heavily-trafficked dimension. Most people live primarily in the Overworld and use the Nether for rapid transport, leaving The End very quiet.
Finally, The End can be made to be very much like the Overworld, and can be set up to provide infinitely renewable sources of almost everything the Overworld has. This includes water, iron, food, trees, stone (and its variant of cobblestone), bone meal, all resources collected from animals (including honey, wool and meat), and all resources collected from Villager trading (including glass, glowstone, redstone dust, Lapis Lazuli, Bottle o' Enchanting, bows and arrows—which aren't much use in the End, but are still available—armor, tools, enchanted books, stone variants, block of quartz, and more. See "Farming" section for how to gain access to these.