cocos2d in CCLabelBMFont and CCLabelAtlas What is the difference between

In cocos2d in CCLabelBMFont and CCLabelAtlas that layer or wizard can add text, then what is the difference between them?
Reply:
Give you a link, you go and see:
http://ask.fenglepai.com/cclabelttf% E3% 80% 81cclabelbmfont% E5% 92% 8Ccclabelatlas% E4% B9% 8B% E9% 97 % B4% E7% 9A% 84% E5% 8C% BA% E5% 88% AB.html