Mainland China
The term "mainland China" is a geopolitical term defined as a territory governed by the People's Republic of China including islands like Hainan or Chongming, excluding dependent territories of the PRC & other territories within Greater China. By convention, the territories that fall outside of the Chinese mainland include:
Overseas Chinese(华裔,华侨)uses this term to describe someone from ancestral land. Mainly used by Malaysian Chinese or Chinese Singaporean.
Many businesses use "mainland China" since it is for a separate customs territory than Hong Kong & Macau, which are under PRC jurisdiction. The term is also employed in political contexts to avoid specific extension of the political status of either the ROC or PRC. The PRC spoke to itself as the "mainland side" when dealing with the ROC, which it calls the "Taiwan side", while Linguistic communication from ROC officials turn with some using "mainland China" and others simply "China". Legally speaking, the Constitution of the Republic of China differentiates between the "mainland area" and the "free area"; in specific the Additional Articles apply only to the "free area".