Sprite sheets are used to improve the performance of your game, not only reducing the time it takes for the game to load but also improving the performance while the game is running.
Tip
Unfortunately, TexturePacker works with Cocos2d at the time of writing this book, but its use is not supported by SpriteBuilder directly. However, TexturePacker is a great solution when it comes to building sprite sheets effectively. If you wish to use TexturePacker but are currently using the directory method (the default for SpriteBuilder at the time of writing this book), go back and change your style to file extensions.
As mentioned in Chapter 1, Refreshing Our Cocos2d Knowledge, we will be using TexturePacker as the go-to for our sprite sheet creator. TexturePacker is nice for a few reasons:
It allows exporting to Cocos2d with one click
It has auto-scaling (up or down) that supports all resolution types
It makes updating your images later easier to import the images...