Tiled is a desktop application that helps create tile maps from sprite sheets. Ceramic Tile Engine is a library for use with Corona that displays the data from Tiled. Two great tools that work great together. The demo provided with Ceramic has a really nice platform game example.
Tile maps are larger images created from smaller tiles. By using, and reusing, small tiles large environments can be created. Since a single image containing a few small tiles takes up much less memory than the image created with the tiles tile maps are more efficient.
Tiled is an application you can use to create tile maps. Tiled is generic and not tied to any other application or programming language. You’ll use it to build maps and export a text file describing your map. Usually this will be in the Json format.
Here are a few links: