Few ethnic minorities natively speak Turkmen; most ethnic Uzbeks natively speak Uzbek, while most ethnic Russians grow up speaking Russian. Due to their past, Russian has been the language of communication between groups as most Turkmen speak the language to some degree. English and other popular world languages are slowly growing in popularity.
Religion
Nearly 90% of Turkmenistan's population is Muslim and the government strongly stresses this religion as a part of Turkmen identity. Of the remaining 10% most are ethnic Russians practicing Russian Orthodox.
Islam (the name of the religion, whose followers are called Muslims) is a monotheistic religion, whose holy book is called the Qur'an. The Qur'an is believed to be the word of God spoken through the prophet Muhammad from 609-632 CE (Common Era is preferred over AD (Anno Domini or "year of the Lord") since the Islamic world doesn't believe Jesus was the messiah). Islam believes Muhammad was the last prophet sent to earth by God, the last in a long line of prophets, which includes Moses, Abraham, and Jesus among others.
Muslims follow five pillars of their faith: testimony, prayer, alms-giving, fasting, and pilgrimage. These pillars, and other tenants of their faith, can give great structure to their lives as some foods, like pork, are forbidden and every Muslim is expected to pray five times a day. However, the level of participation in each of these pillars and to what degree Islam influences an individual's life varies from person to person and community to community. Generally speaking, Turkmenistan is very liberal in how they practice Islam as their former leader, Saparmurat Niyazov (Turkmenbashi), has been incorporated into the religion to some degree.