The required elements of your application -- biographical information, transcripts, GMAT score, references, and essays -- are standard for all schools. Some ask for more references, some interview everyone, others don't interview at all or only selectively. Some ask for additional biographical summary items such as r?sum?s and cover letters.
The admissions office administration staff will wait for all elements of your application to arrive before acting on them. As with college applications, elements of the application usually come separately from different places. As a rule, the admissions department is organized and approachable and will know which items they are waiting for.
You may get periodic mail or e-mail notices telling you what has and hasn't arrived. Once everything is complete, the file will be read by at least two but up to four or five people -- more when the readers don't immediately agree on its merits. Readers do not see each others' comments.
At least one of the two primary readers will be assigned to read the whole package thoroughly, while subsequent readers may just be referred to specific sections...