The Ahl al-Sunnah generally consider it a sunnah to offer specific evening prayers – the Tarawih –in congregation during the holy month of Ramadan. The Shi’ah, while being commended to offer similar nawafil (recommended prayers), are not allowed to offer them in congregation. This practice of the Shi’ah is in accordance with the orders and sunnah of the Prophet (s).
Brothers and sisters from the Ahl al-Sunnah come together in Tarawih congregations during the early evenings of the month of Ramadan. They stand in prayer and recite the Qur’an, and may Allah reward them for their sincere intentions and actions.
However, the word Tarawih was never mentioned by the Qur’an or the Prophet (s) to describe these extra congregational prayers during the evenings of the month of Ramadan.
It is a well-established fact that the Tarawih, as a congregational night prayer of Ramadan, owes its existence to the order of the second caliph, ‘Umar b. al-Khattab.
Allah's Messenger (ﷺ) said, "Whoever prayed at night the whole month of Ramadan out of sincere Faith and hoping for a reward from Allah, then all his previous sins will be forgiven." Ibn Shihab (a sub-narrator) said, "Allah's Messenger (ﷺ) died and the people continued observing that (i.e. Nawafil offered individually, not in congregation), and it remained as it was during the Caliphate of Abu Bakr and in the early days of 'Umar's Caliphate."
Abdur Rahman bin 'Abdul Qari said,
"I went out in the company of 'Umar bin Al-Khattab one night in Ramadan to the mosque and found the people praying in different groups. A man praying alone or a man praying with a little group behind him. So, 'Umar said, 'In my opinion I would better collect these (people) under the leadership of one Qari (Reciter) (i.e. let them pray in congregation!)'. So, he made up his mind to congregate them behind Ubai bin Ka'b. Then on another night I went again in his company and the people were praying behind their reciter. On that, 'Umar remarked, 'What an excellent Bid'a (i.e. innovation in religion) this is; but the prayer which they do not perform, but sleep at its time is better than the one they are offering.' He meant the prayer in the last part of the night. (In those days) people used to pray in the early part of the night."