How are universities organized?
Over the years universities have gone through a lot of changes. That being said almost all universities are organized in the same way, at least in the United States. If you go overseas you will find that schools are organized differently but the schools in the US pretty much all follow the same model. Certainly there are differences between schools but these differences are fairly small.
The basic organization of universities is that they are divided into faculties. Sometimes the faculties will be called schools or colleges but the basic organization remains the same. The faculties will cover the teaching of a broad subject area like the faculty of science or of engineering. There will be a dean in charge of the faculty who is responsible for the administration of the faculty. At most but by no means all universities when you are admitted to the university you will also be admitted to a faculty as well. That means that if you want to study science for example you will have to be admitted to the faculty of science.
The faculties at a university are divided further into subject areas called departments. In our faculty of science of example it would then be divided into a department of physics a department of chemistry and so on. Each department would have a head whose actual title will vary by university. The department will largely be the ones who decide what will be studied by students who are pursuing degrees in the field. They will also teach courses to students from other departments and faculties who need or want to take courses in the subject.
Just how it is decided what courses you will have to take will be done by a combination of the university administration, the faculty and the department. In most cases the university will set a standard of how many courses a student must take to get a degree and how many of them must be in certain subjects. In some cases they may also require that you take specific courses. The faculty will then determine how many courses you need to take in your specific subject area as well as any additional courses from other departments in the faculty. Finally your department will decide specifically which courses in you major are required for the degree.
One area where the organization of the university will differ greatly from one school to another is when it comes to graduate studies. At some schools graduate degrees are administered by the faculty that is responsible for the subject that you are taking. At other schools there will be a separate faculty that is responsible for all graduate study. The difference is not really all that important but it is something to be aware of when you are applying for grad school.