The document discusses the Indo-European language family, which includes many major world languages such as English, Spanish, Hindi, and Russian. It outlines the 10 major branches of the family including Anatolian, Tocharian, Germanic, Italic, Celtic, Armenian, Balto-Slavic, Hellenic, Indo-Iranian, and Albanian. Additionally, it mentions several extinct Indo-European languages and divides the family into the western Centum and eastern Satem subgroups based on sound changes.