The Seven Ecumenical Councils are foundational events in the history of the Orthodox Church. These councils, which were convened between the 4th and 8th centuries, addressed major theological disputes, seeking to define and preserve the orthodox Christian faith. 

1. First Council of Nicaea (325 AD): The primary issue addressed was the nature of Christ in relation to God the Father, sparked by the heresy of Arius, who taught that the Son (Jesus) was a created being and not co-eternal with the Father. The Council condemned Arianism, affirming that the Son is "begotten, not made, of one essence with the Father." This decision is enshrined in the Nicene Creed, which remains a central statement of faith for Orthodox Christians.

2. First Council of Constantinople (381 AD): This council focused on further clarifying the Nicene Creed, particularly the divinity of the Holy Spirit. The council affirmed that the Holy Spirit is fully God, co-equal with the Father and the Son, in opposition to the Macedonian heresy, which denied the Spirit's full divinity. It also addressed various other theological disputes, including Arianism’s lingering influence. The Nicene-Constantinopolitan Creed, as it became known, is still recited in our Divine Liturgy.

3. Council of Ephesus (431 AD): The central issue at Ephesus was the nature of Christ, particularly his relationship to the Virgin Mary. Nestorius, the Patriarch of Constantinople, argued that Mary should be called "Christotokos" (Mother of Christ) rather than "Theotokos" (Mother of God), implying a separation between Christ’s divine and human natures. The council declared Nestorius' teachings heretical and affirmed the use of "Theotokos," emphasizing that Christ is one divine Person with both a divine and human nature, inseparably united.

4. Council of Chalcedon (451 AD): This council dealt with the controversy surrounding the nature of Christ, particularly the teachings of Eutyches, who denied the distinction between Christ's divine and human natures, proposing that they were merged into one. The council produced the Chalcedonian Definition, which declared that Christ is one divine Person in two distinct natures, fully divine and fully human, without confusion, change, division, or separation.

5. Second Council of Constantinople (553 AD): This council was primarily concerned with the ongoing controversy surrounding the writings of certain early Christian theologians, especially Theodore of Mopsuestia and Ibas of Edessa, whose works were seen as Nestorian. The council condemned certain "Three Chapters" that were seen as heretical, affirming the orthodox understanding of Christ’s nature and condemning Nestorianism once again.

6. Third Council of Constantinople (680–681 AD): This council addressed the Monothelite controversy, which claimed that Christ had only one will, divine, not two distinct wills (divine and human). The council condemned Monothelitism, affirming that Christ possesses both a divine will and a human will, which are united in his divine Person but remain distinct.

7. Second Council of Nicaea (787 AD): The final ecumenical council affirmed the Orthodox practice of venerating icons, rejecting the iconoclast heresy, which sought to destroy religious images. The council declared that icons are venerated, not worshipped, and affirmed that they serve as important tools for teaching and devotion. This decision has been central to our understanding of the role of images in worship.

These councils collectively shaped Orthodox Christian theology, safeguarding the doctrines of the Trinity, the nature of Christ, and the role of the Church in interpreting the faith. Their decisions remain authoritative in the Orthodox tradition and are key to understanding its theological and liturgical identity.