If you want to work for the federal government then you must be prepared to submit all types of information about your personality including all personal information. You will be asked to send more information about yourself depending on work sensitivity.
When you apply for any federal job, you must sign a written agreement to approve this government background check. You can get more information about government sector via Peopletrail.
When you sign this agreement, you will provide a personnel management office (OPM) to conduct a full government background check on your personal life, criminal history, and financial status.
OPM investigators will examine every part of your life, talk to everyone who knows you and interview your previous boss and coworkers to find out more about you and your background.
A government background check also includes a full credit line history to ensure that you are doing well enough in your financial life. You don't need to be a rich man or woman to get a job but, some jobs may include dealing with money or sensitive confidential information and the government wants to ensure that the person will be trusted and money will not be a tempting problem for him.
Investigators from the federal government will provide you with a long detailed questionnaire to answer, this answer will help them determine some key points about your personality and that will be the starting point for their investigation.
For example, if you say that you work at company X then they will go to company X and ask HR about the validity of this information, if that is true then they will start talking to your manager and your colleagues to know more about you.