马克思主义 is the Chinese term for 'Marxism', a political and economic theory developed by Karl Marx and Friedrich Engels. In PRC discourse, it is the official state ideology and is often referenced in contexts of political education, party doctrine, and social theory. The word is a compound of 马克思 (Marx, a transliteration) and 主义 ('-ism', a suffix for doctrines). You'll encounter it in formal, academic, or political texts rather than everyday conversation.