East China is the new economic center of the country.
In the 19th century, after one of the Opium Wars, China was forced to open certain Treaty Ports to foreign trade. The two in this region were Ningbo, which until then had been mainly the port for Hangzhou, and Shanghai, until then an insignificant town strategically positioned near the mouth of the Yangtze. Both developed rapidly after that. By the early 20th century, Shanghai became one of the world's richest and wildest cities.
Then everything went wrong; this region was one of the areas of China that Japan succeeded in conquering, and they suffered horrendously under Japanese rule, 1937 to 1945. Then there were the Chinese Civil War, 1945-1949, the Great Leap Forward in the 50s, and the Cultural Revolution 1966-1976; all caused additional problems in this area.
In the "reform and opening up" since 1978, this area has benefited enormously. Shanghai is again definitely one of the world's greatest cities; Hangzhou, Suzhou and Nanjing are not far behind. All are very modern cities with lots of large new buildings, more under construction, and subway systems either in service or under construction. The entire region is a hive of industry, one of the most prosperous in China. It is a magnet for migrants fom pooer regions seeking work.
As anywhere in China, Mandarin is the lingua franca; nearly everyone can speak it. As elsewhere in China, English is not widespread but some people speak it quite well.
The region does have its own language, called Wu or Shanghainese. This is a populous region and the number of Wu native speakers is large; at 78 million it is rather more than French or Italian. There are local variants of Wu; the standard is that of Suzhou (an older city, capital of the Kingdom of Wu centuries back, and home to many scholars), not that of Shanghai.
Perhaps the commonest way to reach the area is to fly to Shanghai. There are two airports. Pudong is a major international airport with connections all over the world; Hong Qiao handles mainly domestic flights.
The area is also well connected via China's road and rail networks, and there is a Suzhou-Japan ferry.