These individuals are the muslim representatives that bear particular responsibilities to achieve all of the objective and targets which has been ruled to spread the da'wah, inculcate good moral values within themselves and others, as well as to do specific tasks concordant with respective posts.
Talking about responsibilities, we must always be reminded about two exclusive responsibilities that ruled to us since we are born.
"And [mention, O Muhammad], when your Lord said to the angels, "Indeed, I will make upon the earth a successive authority." They said, "Will You place upon it one who causes corruption therein and sheds blood, while we declare Your praise and sanctify You?" Allah said, "Indeed, I know that which you do not know."
As a successive authority... In other words, as caliphs. The one who have control over the world with the God's permission, and responsible to create a better world out of it.
Without blood-shedding incidents.
Using all the ni'mat given to us, for all good purposes.
"And I did not create the jinn and mankind except to worship Me."
We must worship Allah... In other words, we are slave of Allah.
We do what we are told to do.
We don't do anything that we are not told to do.
Such a simple rules or concept, right?
But, mujahadah is still the key factor that allow us to be the caliph on this earth and to be the true slave of Allah.
Last but not least, those persons are not the only one responsible for the agenda ruled by the muslim society. But, it's also for all of us. It's our responsible for to take part of it, not just for to fulfill the agenda and objectives, but also to act as a true caliph and slave of Allah.
Because you are created by Allah, after all.