From the point of Canon Law, the only Christian Churches are the Catholic Church, the Eastern Orthodox Church, the Oriental Orthodox Churches, the Church of the East, Polish National Catholic Church, and most (not all) Old Catholic Churches.
Essentially, anywhere you find all 7 sacraments validly administered, with apostolic succession is a Church. Any other place would be an ecclesial community.
From Vat II, Unitatis Redintegratio / DECREE ON ECUMENISM - Abridged
II. Separated Churches and Ecclesial Communities in the West
It must however be admitted that in these Churches and ecclesial Communities there exist important differences from the Catholic Church, not only of a historical, sociological, psychological and cultural character, but especially in the interpretation of revealed truth.
- Our thoughts turn first to those Christians who make open confession of Jesus Christ as God and Lord and as the sole Mediator between God and men, to the glory of the one God, Father, Son and Holy Spirit. We are aware indeed that there exist considerable divergences from the doctrine of the Catholic Church concerning Christ Himself, the Word of God made flesh, the work of redemption, and consequently, concerning the mystery and ministry of the Church, and the role of Mary in the plan of salvation. But we rejoice to see that our separated brethren look to Christ as the source and center of Church unity. Their longing for union with Christ inspires them to seek an ever closer unity, and also to bear witness to their faith among the peoples of the earth.
- A love and reverence of Sacred Scripture which might be described as devotion, leads our brethren to a constant meditative study of the sacred text. For the Gospel “is the power of God for salvation to every one who has faith, to the Jew first and then to the Greek”.(39)
While invoking the Holy Spirit, they seek in these very Scriptures God as it were speaking to them in Christ, Whom the prophets foretold, Who is the Word of God made flesh for us. They contemplate in the Scriptures the life of Christ and what the Divine Master taught and did for our salvation, especially the mysteries of His death and resurrection.
But while the Christians who are separated from us hold the divine authority of the Sacred Books, they differ from ours - some in one way, some in another - regarding the relationship between Scripture and the Church. For, according to Catholic belief, the authentic teaching authority of the Church has a special place in the interpretation and preaching of the written word of God.
But Sacred Scriptures provide for the work of dialogue an instrument of the highest value in the mighty hand of God for the attainment of that unity which the Saviour holds out to all.