The Church and Its Institutions
(Condensed from the Schaff-Herzogg Encyclopedia)
a. The word "ecclesia" in the New Testament means either the universal church of Christ, or a local congregation.
b. The early Christian church began on the day of Pentecost; and it was at first composed of the disciples whom Jesus had personally gathered. It was a community inside of Judaism, with peculiar worship and government. It was the "ecclesia"; and by this name Paul calls it in his earliest epistles, whether in Palestine or outside.
1 Thessalonians 2:14
Its complete name was the "Church of God," or the "Church of Christ"
Romans 16:16
whether of a single congregation, or of the whole body of believers
c. For church government, see in the encyclopedias the articles on the different denominations.
These are baptism and the Lord's Supper.