The People in the congregation is what constitutes the Church.  The Church is not the Building, but the believers who put their Faith in the Lord.  The Elders and Deacons are to guide the congregation in the ways of the Lord.

What the word Mystery meant in Biblical times was the fact that God revealed to us something which we did not know.  The whole Old Testament was all about the coming of the Lord.  Jesus Christ is the Mystery of Godliness.  He came to earth as the Son of God to save mankind.  We just needed to believe in Jesus and follow what he taught us. 

The Father, Son and Holy Spirit, (The 3 in One/Trinity) are here to guide us through our walk and forgive us of our sins, if we only believe. 

Put your faith in the lord and serve the Lord your God with all your heart, soul and Mind.