The church is described in various ways to help us understand what it is and how Jesus leads his people.
When the church described as a body, Jesus Christ is the head and his people are the body parts. When described as a flock, Jesus is the Good Shepherd and his people are his sheep.
He is the one who leads his sheep and laid down his life for his sheep.
In each church, he has given the role of under-shepherds and servers to care for his flock and to equip the body parts to build up his body. There are two main leadership roles that oversee and have responsibility of the whole church - a shepherding role (which is where we get the term pastor) and a serving role (which is where we get the term deacon). Those who shepherd the church are the elders/pastors, and those who serve are the deacons.
Those who serve in these roles are chosen by the church to oversee, care for, teach, protect and direct the whole church.
There may be other leaders in the church who have responsibility for a part of the church, the particular ministry they are leading, which is under the umbrella of the whole church, of which the elders and deacons oversee.