is there a difference?? (chinese language)?

普通話 (putonghua) = Mandarin

Most people who refer to Mandarin as putonghua are Chinese (people from China, not Taiwan). Thus, the difference between the two would be that Chinese people use write in simplified Chinese whereas Taiwanese write traditional Chinese.

many dialects

mandarin======pu tong hua

no difference.
mandarin=putonghua.
putonghua is the chinese pronunciation of mandarin.

I am not sure of this, but I believe that "putonghua" means "national language" in Chinese. I must tell you that I have not studied Chinese and ran across this word in readings in English about Chinese, so you will want to check this out with other people who are familiar with the language.

Harleigh Kyson Jr.

yup. don't know what it is, but I know there are many different languages called "Chinese" Mandarin and Cantonese are the two most widely spoken. So putonghua must be one of the lesser spoken.