Ecumenical councils are gatherings of church leaders from various Christian denominations to discuss and resolve important theological and doctrinal issues. These councils aim to promote unity and address disputes within the Christian faith. Notable examples include the First Council of Nicaea in 325 AD, which established foundational Christian doctrines. During these councils, representatives debate and vote on key topics, such as the nature of Christ or the authority of Scripture. The decisions made can lead to significant changes in church practices and beliefs, influencing the direction of Christianity as a whole.