There are currently two types of Chinese script in use. The complicated style, also known as the traditional style, is used in regions that were not under the control of the Chinese Communist Party in 1949, including Taiwan, Hong Kong and Macau. The simplified script is used in mainland China.

The traditional style is the script that has been slowly developed through the millenia of Chinese history, beginning with the Zhou Dynasty, when the pictogram system came into use. The evolution of the Chinese script never stopped, there are characters used in the early Qing Dynasty that were obsolete at beginning of this century. Hence the annoyance of reading medieval Chinese (old Chinese), because you don't know half the characters.

The CCP, intent on spreading literacy to the masses, simplified the bloated system. It essentially turned the script into a type of shorthand, many redundant strokes were removed, parts that were often used were watered down. For example, the character for eat, chi, originally contains 9 strokes, the new version needs only 3:

Complicated: 食
Simplified: ⻠

This makes Chinese easier to learn. However, whereas the old character actually had some semblance of meaning to it (characters were pictograms, they still look like the things they're supposed to represent sometimes), the new ones are meaningless symbols.

The Chinese literati cried out for the death of a national relic, for many people take pride in their language, with millenia of evolution behind it. People still often use the traditional script, especially for calligraphy, but the simplified script is the one taught in schools. Hong Kong and Taiwan are extremely stubborn with their educational systems, because they feel the need to differ themselves with the mainland Chinese, whom they falsely perceive to be inferior. However, the integration of the two scripts is inevitable.

Personally, I prefer the simplified script. The traditional style gives me headaches trying to remember all the brush-strokes.