In the first century, early Christians gathered for prayer, worship, and the celebration of the Eucharist in private homes, which were called “house churches.”
This continued during the persecutions that followed, from the time of Emperor Nero (64 AD). During these times, Christians also gathered for worship in catacombs or underground burial sites.
The first homes or buildings converted into dedicated churches began to appear in the early part of the third century.
With the conversion of Emperor Constantine (312 AD) and the edict of Milan (313 AD), which proclaimed official toleration of the Christian faith, Christians were finally free to worship openly. New church buildings were constructed on the same design as Jewish synagogues or on the design of the Greco-Roman basilica, which was common building at the time, used for courts and other government functions.
Any building consecrated for worship was called a “Church,” a “House of God,” or a “Temple of God.”