The end city is a special finite structure. It is one of the interesting places to explore, since it is invaded by shulkers.
And it is the only place where you can find the elytra, an incredibly useful pair of wings. You can use these wings to fly.
The end cities are a perfect place to go before making long trips. Eat Chorus Fruit to stay alive if you’re going to teleport.
To get home use the portals of the End Gateway. To cross them, you’ll need an ender pearl. The End Gateway rarely appears on outer islands.
The Outer End Islands can be found next to End Gateway. If you can’t find one you have to move back to your original position (or go back to the island’s main).
You can also place your most precious stuff in the chest if you find an Ender Chest in End Zone, then leap into the void to get back to the world (assuming you are not in hardcore mode).