Pinyin is similar to phonetic symbol in english which marks the pronunciation of words, e.g. 你好/nǐ,haǒ/ <-pinyin
Pinyin built up with Latin alphabets was standardized in 1958 by China government for Mandarin Chinese, here is a web to learn Pinyin: http://www.newconceptmandarin.com/support/Intro_Pinyin.asp
注音 created about 100 years ago is the old way to mark pronunciation of Chinese which was abandoned in 1958 by China mainland but still alive in Taiwan and some other places where the local people use Traditional Chinese.
is it helpful?