Like many Asian languages, Chinese is a tonal language. This means that a word can have various meanings depending on the tone used to pronounce it. There are four tones in Mandarin Chinese which are represented by the four tone marks over the vowels in pinyin.
Before you go any further with your learning, Dani gives you a lesson dedicated to understanding and using the tones. It is possible to relate the concept of tones to how you use the tone of your voice in speaking English. For example the tone of your voice will often change when asking a question or giving an order in English!