What Is the Church? Person, Place, or Thing?

What is the church? Is the church a building? Is it the place where believers gather to worship? Or is the church the people—the believers who follow Christ? How we understand and perceive the church is an important factor in determining how we live out our faith.
For the purpose of this study, we will look at the church in the context of "the Christian church," which is a New Testament concept. Jesus was the first person to mention the church:
Simon Peter replied, “You are the Christ, the Son of the living God.” And Jesus answered him, “Blessed are you, Simon Bar-Jonah! For flesh and blood has not revealed this to you, but my Father who is in heaven. And I tell you, you are Peter, and on this rock I will build my church, and the gates of hell shall not prevail against it. (Matthew 16:16–18, ESV)

Some Christian denominations, such as the Catholic Church, interpret this verse to mean that Peter is the rock upon which the church was founded, and for this reason, Peter is considered the first Pope. However, Protestants, as well as other Christian denominations, understand this verse differently.
Although many believe Jesus noted the meaning of Peter's name here as rock, there was no supremacy given to him by Christ. Rather, Jesus was referring to Peter's declaration: "You are the Christ, the Son of the living God." This confession of faith is the rock upon which the church is built, and just like Peter, everyone who confesses Jesus Christ as Lord is a part of the church. Have you ever wondered, why the Church is called the body of Christ and not Jesus?

Church Definition in the New Testament
The word "church" as rendered in the New Testament comes from the Greek term ekklesia which is formed from two Greek words meaning "an assembly" and "to call out" or "called out ones." This means the New Testament church is a body of believers who have been called out from the world by God to live as his people under the authority of Jesus Christ:
God has put all things under the authority of Christ and has made him head over all things for the benefit of the church.
And the church is his body; it is made full and complete by Christ, who fills all things everywhere with himself. (Ephesians 1:22–23, NLT)
This group of believers or "the body of Christ" began in Acts 2 on the Day of Pentecost through the work of the Holy Spirit and will continue to be formed until the day of the rapture of the church.

Becoming a Member of the Church
A person becomes a member of the church simply by exercising faith in Jesus Christ as Lord and Savior.

The Church Local Versus the Church Universal
The local church is defined as a local assembly of believers or a congregation that meets together physically for worship, fellowship, teaching, prayer and encouragement in the faith (Hebrews 10:25). At the local church level, we can live in relationship with other believers—we break bread together (Holy Communion), we pray for each other, teach and make disciples, strengthen and encourage one another.
At the same time, all believers are members of the universal church. The universal church is made up of every single person who has exercised faith in Jesus Christ for salvation, including members of every local church body throughout the earth:
For we were all baptized by one Spirit so as to form one body—whether Jews or Gentiles, slave or free—and we were all given the one Spirit to drink. (1 Corinthians 12:13, NIV)

The founder of the home church movement in England, Canon Ernest Southcott, defined the church best:
"The holiest moment of the church service is the moment when God’s people—strengthened by preaching and sacrament—go out of the church door into the world to be the church. We don’t go to church; we are the church."
The church, therefore, is not a place. It's not the building, it's not the location, and it's not the denomination. We—God's people who are in Christ Jesus—are the church.

The Purpose of the Church
The purpose of the church is two-fold. The church comes together (assembles) for the purpose of bringing each member to spiritual maturity (Ephesians 4:13).
The church reaches out (scatters) to spread the love of Christ and the gospel message to unbelievers in the world (Matthew 28:18-20). This is the Great Commission, to go out into the world and make disciples. So, the purpose of the church is to minister to believers and unbelievers.
The church, both in the universal and local sense, is important because it is the primary vehicle through which God carries out His purposes on earth. The church is the body of Christ—His heart, His mouth, His hands, and feet—reaching out to the world:
Now you are the body of Christ, and each one of you is a part of it. (1 Corinthians 12:27, NIV)

Extract from ThoughtCo