An ecumenical council is a gathering of bishops from various Christian churches, called together to discuss and make decisions on matters of faith, doctrine, and church practice. These councils are considered authoritative and their decrees are binding on the whole Church. The term "ecumenical" refers to the universal nature of these councils, as they represent the entire Christian Church rather than a single denomination or tradition. Some of the most well-known ecumenical councils include the First Council of Nicaea (325 AD), the Second Council of Constantinople (553 AD), and the First Vatican Council (1869-1870).