What's behind the founding ceremony of the PRC?

At 3:00 pm on October 1, 1949, the founding ceremony of the People's Republic of China was held on Tian'anmen Square in Beijing. The first Chinese leader Mao Zedong announced, "The People's Republic of China and the Central People's Government are now established!" Mao pressed a button, and the Five-Starred Red Flag began to rise slowly. Since then, China has entered a new era.