Mainland China (中国大陆 or 中國大陸, pinyin: Zhōnggúo Dàlù, lit. "The Chinese Massive Landmass" or "Continental China"), is an informal geographical term which is usually synonymous with the area currently administered by the People's Republic of China (PRC) which excludes the area controlled by the Republic of China (ROC), namely Taiwan, Penghu, Quemoy, Matsu islands. It also usually excludes the two special administrative regions administered by the People's Republic of China: Hong Kong and Macau. In contrast to the term China proper, the term usually also includes Tibet, Xinjiang, and Inner Mongolia.
Curiously, the term usually includes offshore islands administered by the PRC such as Hainan. The term Zhongguo dalu is commonly used on Taiwan because it is a neutral term and does not contain implications about the political status of Taiwan.
More recently, the term Zhongguo neidi (內地 "the inner regions of China") has become the most common term within Mainland China to refer to Mainland China, although the term is infrequently used outside of Mainland China.
In Taiwan, the term Mainlander can refer to wai sheng ren (外省人, literal meaning: "external province person(s)"), who are the people who emigrated to Taiwan from Mainland China near end of the Chinese Civil War. Or the term can refer to da lu ren (大陸人, literal meaning: "Mainland person(s)"), meaning the people who live on the Mainland now.
Relations between Mainland China and Taiwan are typically known in Chinese as liang'an guanxi (兩岸關係), which literally means "relations between the two sides/seashores (of the Strait of Taiwan)". The term liang'an (two sides) is often used when describing Mainland China and Taiwan collectively. Again these terms are commonly found because they are politically-neutral and do not contain implications about the nature of the relationship between Mainland China and Taiwan.
See also: Mainland