Short answers, pulled from the story.
There are 23 Eastern Catholic Churches, all in full communion with the pope in Rome. Of the 1.3 billion Catholics worldwide, approximately 18 million belong to these Eastern churches, making them a minority within the broader Catholic Church.
As of 2022, the Syro-Malabar Church is the largest Eastern Catholic Church, followed by the Ukrainian Greek Catholic Church. The six largest Eastern Catholic churches together account for about 85 percent of total Eastern Catholic membership.
The five historic liturgical traditions represented within Eastern Catholic liturgy are the Alexandrian Rite, the Armenian Rite, the Byzantine Rite, the East Syriac Rite, and the West Syriac Rite. Each rite carries its own liturgical, theological, spiritual, and disciplinary heritage.
Most Eastern Catholic Churches allow the ordination of married men as priests, though not as bishops. In Ukraine, 90 percent of diocesan priests in the Ukrainian Greek Catholic Church are married. Some Eastern Catholic churches, including the Syro-Malankara Catholic Church and the Coptic Catholic Church, have adopted mandatory clerical celibacy similar to the Latin Church.
The Balamand Declaration is a 1993 document submitted by the Joint International Commission for Theological Dialogue Between the Catholic Church and the Orthodox Church. It concluded that the historical method of forming Eastern Catholic churches by drawing communities away from their Orthodox mother churches, known as uniatism, can no longer be accepted as a model of Christian unity, while affirming the right of existing Eastern Catholic churches to continue serving their faithful.
The Code of Canons of the Eastern Churches was promulgated in 1990 and took effect in 1991. It was the first codified body of canon law governing all Eastern Catholic Churches collectively, providing a shared framework while each individual church retains its own internal canons layered on top.