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

Others look at it as action that Christian people do when ever they visit the physical building.

Some Believe

The Bible tells us the church or the body is called out by God

We have different gifts, according to the grace given to each of us. If your gift is prophesying, then prophesy in accordance with your[a] faith; 7 if it is serving, then serve; if it is teaching, then teach; 8 if it is to encourage, then give encouragement; if it is giving, then give generously; if it is to lead,[b] do it diligently; if it is to show mercy, do it cheerfully.

Romans 12:6-8

The Church (Body of Christ/ Believers) was given gifts to edify, develop and help its members.  Let's look at what the scriptures says about those gifts.

Some look at the definition of the Church as the building where religious congregate.

The Church

Some look at the definition of the Church as the building where Christians congregate.

11 So Christ himself gave the apostles, the prophets, the evangelists, the pastors and teachers, 12 to equip his people for works of service, so that the body of Christ may be built up 13 until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ.

Ephesians 4:11-13

The Church

25) so that there should be no division in the body, but that its parts should have equal concern for each other. 26) If one part suffers, every part suffers with it; if one part is honored, every part rejoices with it. 27) Now you are the body of Christ, and each one of you is a part of it.

What and who is the church?

And God has placed in the church first of all apostles, second prophets, third teachers, then miracles, then gifts of healing, of helping, of guidance, and of different kinds of tongues.

1 Corinthian 12:27-28

There are different kinds of gifts, but the same Spirit distributes them. 5 There are different kinds of service, but the same Lord. 6 There are different kinds of working, but in all of them and in everyone it is the same God at work.
7 Now to each one the manifestation of the Spirit is given for the common good. 8 To one there is given through the Spirit a message of wisdom, to another a message of knowledge by means of the same Spirit, 9 to another faith by the same Spirit, to another gifts of healing by that one Spirit, 10 to another miraculous powers, to another prophecy, to another distinguishing between spirits, to another speaking in different kinds of tongues,[a] and to still another the interpretation of tongues.[b] 11 All these are the work of one and the same Spirit, and he distributes them to each one, just as he determines.

1 Corinthian 12:4-11

Others look at it as action that religious people do whenever they visit the physical building.