The U.S. Federal Government is a mammoth organization with jobs ranging from astronaut to zoologist and everything in between.
As with most large organizations, policies and practices try to ensure consistency across all parts.
When an organization is over 200 years old, those policies can be mammoth, too.
The U.S. Federal Government has a formal, methodical hiring process which tries to ensure fairness to all. This means many rules that must be followed, and a standardized process that must be navigated very carefully.
Given the age of this organization, the process isn't simple, but it is well-documented. Job-Hunt will try to break the process down into understandable steps, and guide you through it.
Good luck with your job search!