Most of the ethnic Russians speak Russian and few learn Estonian. This makes Russian the primary language of communication as much of Estonia's older population is fluent in Russian from the Soviet times. However today the ethnic Estonians are learning Russian in smaller numbers, often times at the expense of learning English, which is slowly becoming the second language of choice and the primary means of communication between linguistic groups (although many ethnic Russians and older people don't speak English).
Religion
Most of Estonia's population is either religiously unattached or doesn't strongly adhere to any particular religion. For those who do practice, Evangelical Lutheran is the most populous religion, followed by Orthodox, which is primarily practiced by ethnic Russians.
Lutheranism is a protestant religion that was founded by and named after Martin Luther, who led the Protestant Reformation. Like all Christian and protestant faiths, Lutherans believe there is one God and that His son, Jesus is the savior and forgiver of sins. Lutherans also believe that the Bible, which includes the Old and New Testaments, is the only true word of God. It is generally in the interpretation of the Bible that protestant religions vary and this is true in the case of Lutheranism, which tends to interpret the Bible quite differently from Catholicism, which was the religion Lutheranism separated from.