All will face the same problem when learning a new language - new vowels and consonants we have never use before. Not like German, French or English that has less than 30 litters to compose all words, Chinese has thousands of characters. One character in Chinese is not a letter in English. One character has its own meaning. We know how to read a new German word without looking up the dictionary while we can’t in Chinese. We use Pinyin(拼音) to annotate the sound of a Chinese character.
A simple answer is people in China.
When we say “speak Chinese”, “Chinese” means Standard Chinese, Mandarin, Putonghua (普通话). Besides Mandarin, people speak some dialects in different parts of China. For example, most people living in Guangdong(Canton) province speaks Cantonese. But not all people living in Canton speaks Cantonese. Teochew and Taishanese are also important dialects in Canton. You may hear them in Chinatown all over the world. Don't panic if you have learnt Chinese for a long time and find that you can't understand what local people are saying.
This tutorial is a quick start for learning Chinese. You will know about basic knowledge about Chinese language and its culture that benefit your travel or business in China.