Politics

Controlling something as vast as China was not possible, at least not indefinitely. Various Chinese dynasties rose and fell due to the same power struggles that have persisted. Empires required to have a strong, central authority often in the north (Beijing). Maintaining control over the Guangdong in the south was hard due to the hilly jungles, the distance from the main seat of power and the various non-Han populations (Guangxi & Yunnan as an example).

Foreign Attitude

Historically

China viewed itself as the 'Middle Kingdom', an entity with a superior culture compared to its neighbors. Chinese dynasties ruled with divine favour with the Mandate of Heaven and sought to rid of its 'barbaric' neighbors by having their peoples adopt Chinese culture. Confucian ideas emphasized authority and order, which helped shape Chinese politics. It also had an extensive tribunary system, having surrounding kingdoms as vassals and having them pay tribute to Imperial China.

Now

The People's Republic of China or Modern China wants to be seen as a peaceful, powerful nation that wants nothing but to establish mutually beneficial relations. An example of this is the Belt and Road initiative otherwise known as the New Silk Road, which is an initiative led by China that aims to create smoother, better trade routes by funding various infrastructure projects from Asia to Europe to Africa.

It also, typically, doesn't meddle with the internal affairs of other countries. With the Century of Humiliation which imposed a line of unequal treaties and wars (Opium Wars) that aimed to belittle Qing China's power altogether, China decided to respond by respecting the sovereignty of other nations with non-interference.

Ideology

Today, China is communist and justifies its rule with economic growth and internal stability. Maoism, named after political leader Mao Zedong, founder of modern China, focuses on revolution and self-reliance by sustaining yourself without the need of others.

After the death of Mao Zedong, Deng Xiaoping took hold of the country and helped open up its market allowing for private companies (with state supervision) to form. The Deng Xiaoping Theory, an ideology established by Deng Xiaoping, sought to maintain China's socialist ideals (for example eliminating poverty) by using capitalist methods to achieve said ideals.

Power structure in the Chinese Communist Party

The Central Committee holds the highest form of central authority within the country. It's comparable with a parliament, responsible for the policies that dictate how the CCP rules. Similar to other communist structures, such as the one of the USSR, there's a select group within the Central Committee called the Politburo representing the most powerful people within the Central Committee. Even further divided stands the Politburo Standing Committee, this group, including the General Secretary, hold absolute control over the Central Committee aswell as holds complete authority over China's defense, headed by the Central Military Commission.