"This is a true saying, If a man desire the office of a bishop, he desireth a good work." 1 Timothy 3:1 KJV
The first and most important part of the church’s organization is the Head Shepherd who is Jesus Christ (Ephesians 1:22-23, 4:15-16; 1 Corinthians 12:12-13). He is the one who joins and holds every part of the church’s body together. Without Jesus as the head of the church, it will not be able to function or accomplish its mission.
Underneath the Head Shepherd, there is a group of under shepherds (overseers, elders or pastors) who are the spiritual leaders of the church. This group of spiritual leaders can be composed of some individuals who have dedicated their livelihoods to ministry and others who do not and make a living elsewhere. Their primary focus is to oversee the spiritual aspects of the church. We can see with the early church in Acts 6:1-4 that, in addition to spiritual matters, the twelve apostles also encountered other things that needed attention in the church.
Now in these days when the disciples were increasing in number, a complaint by the Hellenists arose against the Hebrews because their widows were being neglected in the daily distribution. And the twelve summoned the full number of the disciples and said, “It is not right that we should give up preaching the word of God to serve tables. Therefore, brothers, pick out from among you seven men of good repute, full of the Spirit and of wisdom, whom we will appoint to this duty. But we will devote ourselves to prayer and to the ministry of the word.” (ESV®)
This passage shows that the twelve apostles saw their need to stay focused on the spiritual matters of ministry. So they created deacons (which means “servant”) to support and serve the spiritual leadership and the church by taking care of the other primarily physical aspects of ministry. Today these things can include church finances, support staff, maintenance of the church’s property, custodial, technical ministries, and other “helps” or service ministries. This allows the spiritual leadership to not become preoccupied by these other things that need to be taken care of in the church. There is a natural tendency to get pulled into focusing on the physical world around us and end up neglecting the more important spiritual matters of the church.