The Church is the assembly of the believers (1 Corinthians 14:23). The bible doesn't talk about a church but "the church" and the "church of the living God" (1 Timothy 3:15, ASV). All those who are born again are part of it. It is the body of Christ, Jesus is its head (Colossians 1:18).
Paul said to the christians in Corinth : "Now you are the body of Christ, and members individually." (1 Corinthians 12:27, NKJV). So the church is not a building but a living body with its "members".
The church is also "the pillar and ground of the truth", and "the house of God" (1 Timothy 3:15, NKJV)).