It is a synonym for ummat al-Islām (أمة الإسلام, 'the Islamic community'), and it is commonly used to mean the collective community of Islamic peoples. In the Quran the ummah typically refers to a single group that shares common religious beliefs, specifically those that are the objects of a divine plan of salvation. In the context of pan-Islamism and politics, the word ummah can be used to mean the concept of a Commonwealth of the Believers (أمة المؤمنين ummat al-muʼminīn).
The word Ummah (pl. umam) means Nation in Arabic. For example the Arabic term for the United Nations in Arabic is الأمم المتحدة Al-Umam Al-Mutahedah, and the term الأمة العربية Al-Ummah Al-Arabeyah is used to refer to "The Arabic Nation". 
The Word Ummah differs from the concept of a country or people. In it is greater context it is used to describe a larger group of people. For example, in Arabic the world شعب Sha'ab ("people") would be used to describe the citizens of Turkey. However, the term Ummah is used to describe the Turkic Nation as a whole, which includes Turkey, Turkmenistan, Kazakhstan, Azerbaijan, and other countries and ethnic groups in Central Asia.
The phrase Ummah Wāhidah in the Quran (أمة واحدة, "One Nation") refers to all the Islamic world as it existed at the time. The Quran says: "You are the best nation brought out for Mankind, commanding what is righteous (معروف Ma'rūf, lit. "recognized ") and forbidding what is wrong (منكر Munkar, lit. "recognized ")" .
The usage is further clarified by the Constitution of Medina, an early document said to have been negotiated by Muhammad in CE 622 with the leading clans of Medina, which explicitly refers to Jewish, Christians and pagan citizens of Medina as members of the Ummah.
At the time of Muhammad, before the conception of the ummah, Arab communities were typically governed by kinship. In other words, the political ideology of the Arabs centered around tribal affiliations and blood-relational ties. In the midst of a tribal society, the religion of Islam emerged and along with it the concept of the ummah. The ummah emerged according to the idea that a messenger or prophet has been sent to a community. But unlike earlier messengers who had been sent to various communities in the past (as can be found among the Prophets in the Old Testament), Muhammad had been given the task to develop a universal ummah and not only for the Arabs. Muhammad's purpose as messenger to them was to transmit a divine message, and lead the Islamic community to salvation. Since Muhammad is the messenger for the ummah, it indicates there is a divine message, which further implies that God is directing the life affairs of the ummah. Accordingly, the purpose of the ummah was to be based on religion, following the commands of God, rather than kinship.