The term "church" is used in two senses in the scriptures. There is the universal sense and there is the local sense. In the universal sense the church is made up of all those who have been born again of the Spirit of God, and have by that same Spirit been baptized into the body of Christ (I Cor.12:13; I Pet,1:3,22-25). Christ said 'I will build my church' (not churches) Mat.16:18. The Apostle Paul was grieved because he had persecuted 'the church' (I Cor 15:9; Gal.1:13; Phil.3:6). In these examples the Greek word that is used is ekklesia, which simply means 'the called out ones'. The church is also called the 'bride of Christ'. And in that sense she is espoused to Christ, and is to be faithful to Him. The church has been called out from the world, separated from sin, and united to Christ her Head and Sovereign Lord.
In the 'local' sense the word church is used of a group or body of professing believers in a particular locality. We read of the church in Jerusalem in Acts 8:1. We read of the church in Ephesus in Acts 20, the church in Corinth, and many other examples. And though on a smaller scale the local church is to be a replica of the larger universal church.
The purpose of the church is to meet together at regular scheduled times for worship, teaching from the Word, and fellowship of the saints. It also meets together for the observance of the ordinances, prayer, and when necessary discipline. The church is to preach the gospel to those that are lost.
The governing of the local church is to be by oversight of a group of appointed elders. No where in scripture do we read of a hierarchy of clergy, only elders. There is no separate priestly class, but one body, a priesthood of all believers, with Christ as the head.
For where two or three are gathered together in my name, there am I in the midst of them. Matt.18:20