Short answers, pulled from the story.
Nicholas of Cusa (1401-1464) was a German Catholic cardinal, philosopher, theologian, mathematician, and astronomer. He is best known for his concept of "learned ignorance," his early arguments that the earth is not the center of the universe, and his proposal of an election method equivalent to the modern Borda count. He was one of the first German proponents of Renaissance humanism.
Learned ignorance, developed in his 1440 treatise De Docta Ignorantia, is the idea that the finite human mind cannot fully know the infinite divine mind. By clearly recognizing the limits of what the mind can know, a person attains a sophisticated form of wisdom. The concept draws on neoplatonism and negative theology, particularly the writings of Pseudo-Dionysius the Areopagite.
Nicholas argued that the earth is a star like other stars, is not at rest, is not the center of the universe, and has poles that are not fixed. He also held that celestial bodies are not perfectly spherical and their orbits are not perfectly circular. The 1913 Catholic Encyclopedia noted that had Copernicus known of these claims, he would likely have been encouraged to publish his own work sooner.
The Borda count is a ranked voting method in which candidates receive points based on voters' preference rankings. Nicholas of Cusa proposed an essentially identical system in 1433 as a method for electing Holy Roman Emperors. His proposal preceded the work of Jean-Charles de Borda by more than three centuries, and the method is still used in academic institutions, competitions, and some political jurisdictions.
Duke Sigismund of Austria imprisoned Nicholas in 1460 during a dispute over diocesan reforms and revenues in the Bishopric of Brixen. Pope Pius II responded by excommunicating Sigismund and placing an interdict on his lands. Nicholas escaped and returned to Rome but was never able to return to his bishopric. He died at Todi in Umbria on the 11th of August 1464; Sigismund's capitulation came only a few days later.
Shortly after the fall of Constantinople in 1453, Nicholas wrote De pace fidei, imagining a heavenly conference where representatives of all nations and religions agreed on one faith expressed in different rites. He also wrote Cribratio Alchorani, a detailed review of the Quran in Latin based on Robert of Ketton's twelfth-century translation, which credited Judaism and Islam with partially sharing in truth while arguing for Christianity's superiority.