What is the difference between Agency, Department and business unit?
The term Agency refers to a whole organisation, for example Northern Territory Treasury, Department of Business and Employment and Department of Planning and Infrastructure. ‘Agency’ and ‘Department’ are used interchangeably. A business unit is an area within an Agency that has specified functions and contributes to the output of that Agency. To see the business units that form part of Northern Territory Treasury see Treasury business units for more information.
I really love coding and even work in this area, I always try to learn more about my profession or about the IT field, and recently I heard about infrastructure as a code, and I decided to find more material about this topic, it was difficult, but I still figured it out in this topic thanks to one article, here is a link to it https://deepinspire.com/blog/what_is_infrastructure_as_code is really a very complex and important topic in our world, I recommend reading it!
In essence, they are just different forms of organization or business.
So, an agency is a certain institution, an organization that is engaged in-state, public or social work with the population and, of course, makes a profit from the number of services provided. If several decades ago our humanity did not really need such organizations, today it has already become a necessity. 
