From wikipedia: Simplified Chinese Characters (simplified Chinese: 简化字; traditional Chinese: 簡化字; pinyin: Jiǎnhuàzì) are one of two standard sets of Chinese characters of the contemporary Chinese written language. They are based mostly on popular cursive (caoshu) forms embodying graphic or phonetic simplifications of the traditional forms that were used in printed text for over a thousand years. The government of the People's Republic of China has promoted them for use in printing in an attempt to increase literacy. They are officially used in the People's Republic of China (Mainland China), Singapore, and the United Nations. Traditional Chinese is currently used in the Republic of China or Taiwan, Hong Kong and Macau. Overseas Chinese communities generally use traditional characters, but simplified characters are often used among mainland Chinese immigrants. However, the majority of the Chinese-speaking world uses simplified characters. Simplified character forms were created by decreasing the number of strokes and simplifying the forms of a sizable proportion of traditional Chinese characters. Some characters were simplified by applying regular rules; for example, by replacing all occurrences of a certain component with a simpler variant. Some characters were simplified irregularly, however, and some simplified characters are very dissimilar to and unpredictable from traditional characters. Finally, many characters were left untouched by simplification, and are thus identical between the traditional and simplified Chinese orthographies.

i am foreign student in china! most of my friends use simplified chinese! we also learn simplified chinese! they can understand traditional chinese but not much! normaly chinese people dont know traditional! even my chinese language teacher dont know fully traditional language!

繁体文字现在在台湾和香港还在用，大陆不用了。但是基本的繁体字大陆人还是可以看懂的。