The church in Acts is a Spirit-filled fellowship made up of men and women whose lives have been transformed by the power of God.  What is true of the church cannot be explained in human terms, nor can it be manufactured by man.  Rather, the fellowship of the church as described here in Acts 2 is the visible, outward display of the invisible, inward life of God that unites the believers in Christ.  That’s what sets the church apart from anything else.