Reliable sources with information about Myanmar include the CIA website, at which the country is listed under its old name of Burma, as well as Wikipedia and the BBC website. These sites give information about the country's government, political situation, economy and geography.
The sources also give information about the ethnicities and religions of the people of Myanmar. As of 2015, according to the CIA's website, the population was 56,320,206. The official language was Burmese, though ethnic minorities spoke their own languages. Most people were Buddhists, followed by Christians, Muslims, animists and others.
The Wikipedia page goes into detail about the country's history, including its dynasties, its time as part of the British empire and as a military dictatorship.