A sprite sheet packs a number of smaller images into a single large image.
The placement of the smaller images are defined by a json file. The larger image and json file is typically created by a tool such as TexturePacker. The SpriteSheet class will take a reference to a larger image and a json string. From the image and the string the SpriteSheet creates a number of SpriteTexture objects. The names of the frames in the sprite sheet definition are used to reference the different textures.