The 2D Map allows you to interactively manage chunks from your Minecraft world. As well as change texture packs. If your Minecraft saves world directory is missing or cannot be found, Chunky will prompt you for a location of your world saves. You can also specify a certain world as well.
Chunky can be run along side with Minecraft, meaning you can have both open at the same time. This allows you to walk around your worlds and setup renders based on your character's position. However, it is recommended to exit any other programs (including Minecraft) when you render your image.