I was wondering how to do this, because I had gotten a new computer, and didn't want to give up my Minecraft world on my old computer. So, this is how. You are going to need a storage device, maybe a DVD or a flash drive. Go to the search on your computer (bottom left hand corner on Windows) and type in %appdata% (add the %'s) and hit enter. A window should pop up, with a folder named .minecraft. Open that folder, and you should see another folder inside that one named Saves. Double click on that folder, and then you should see folders named World(Whatever number your world is). For instance, world 1 would be named World1. If you wanted to transfer World1 to a different computer, you would just right click on the folder, and hit copy. Go into your flash drive folder, right click, and hit paste. This should paste the Minecraft world onto the flash drive. Take out the flash drive, put it into the computer you want the Minecraft world on, go into the flash drive folder, copy the Minecraft world, and find the saves folder on that computer, inside the .minecraft folder. If there is another world named World1, it won't work. you can't have another world named the same. Once you're in the Saves folder, paste the Minecraft world you copied from the flash drive. After you do that, you should have the world on that computer. If you have any questions or comments, please post them on this topic, and I should look for it. Glad to be of service to help anyone out!
Thank you this is so helpful! I really wanna start building a world but I'm getting a new computer soon so I wanted to make sure I wouldnt have to start over and have all my work be pointless. So thanks. Also, can you rename worlds? So you don't run into that problem you talked about with having two worlds with the same name?
Thankyou so much! This was very helpful, I will like it immediately. By the way, if all your computers are connected to a network, instead of using a Flash Drive, you could just create a folder in your network and then re-open that in your other computer, re-saving your worlds in your new .minecraft folder.