Is performing the Tarawih prayer in congregation a Bid‘ah (innovation), and was it initiated by Umar ibn al-Khattab?

Tarawih prayer is not an innovation (bid'ah); rather, it is a Prophetic Sunnah. The Prophet, peace and blessings be upon him, prayed it with his Companions for several nights, then he left it fearing that it might be made obligatory upon them. This fear ceased with his passing, peace and blessings be upon him. What Umar ibn al-Khattab, may Allah be pleased with him, did was to revive this Sunnah after the revelation had ceased.