More than 130 political appointees working in the Executive Office for President Trump do not have permanent security clearances. Some of the staffers on the list who have access to classified materials—including material designated as “top secret, sensitive compartmented information”—but do not have a clearance include the president’s daughter, son-in-law, and his top legal counsel, reports NBC News. About a quarter of all political appointees in the executive office are working with some form of interim security clearance.

Here is what you should know about security clearances:

What is a security clearance?

A security clearance is a determination by the United States government that a person or company, whether a federal employee or contractor, is eligible for access to classified national security information.

Can anyone with a security clearance access classified information?

No. A security clearance means that an individual is eligible for access. (The term “eligibility for access” means the same thing as security clearance.) To gain access to specific classified materials, an individual should also have demonstrated a “need-to-know” the information contained in the specific classified materials.

What are the levels of security clearance?

There are three levels of security clearances: Confidential, Secret, and Top Secret. Each corresponds to the levels of sensitivity of the information that a cleared individual will be eligible to access. The three classification levels for national security information are:

Confidential—applied to information, the unauthorized disclosure of which reasonably could be expected to cause damage to the national security that the original classification authority is able to identify or describe.

Secret—applied to information, the unauthorized disclosure of which reasonably could be expected to cause serious damage to the national security that the original classification authority is able to identify or describe.

Top Secret—applied to information, the unauthorized disclosure of which reasonably could be expected to cause exceptionally grave damage to the national security that the original classification authority is able to identify or describe.

Is all classified material treated the same based on the classification?

No. In addition to the three classifications, there are two major categories of classified information that require additional handling and access restrictions—Sensitive Compartmented Information (SCI), which includes intelligence sources, methods, and processes, and Special Access Program (SAP), which are programs established for a specific class of classified information that imposes safeguarding and access requirements that exceed those normally required for information at the same classification level.

Eligibility standards and investigative requirements for access to SCI and SAPs are higher than for access to information otherwise classified at the same level.

How does a person obtain a security clearance?

The first step is for a sponsoring federal agency to initiate the security clearance for a person who has a need-to-know the information. An agency head or the agency head’s designee must first make a favorable determination of eligibility for access. The agency will have the individual fill out clearance application materials, including an approved nondisclosure agreement and a Standard Form 86—SF86 (Questionnaire for National Security Positions).

These materials will be used during the background investigation. The level of scrutiny for this background check varies based on the level of clearance. After the background check is completed, the investigators provide the results of their investigation to the agency, which has the final authority to decide if the clearance will be granted.

What criteria are considered when approving a security clearance?

The primary adjudicative guidelines that federal adjudicators use when making security clearance determinations are: (1) Allegiance to the United States; (2) Foreign Influence; (3) Foreign Preference; (4) Sexual Behavior; (5) Personal Conduct; (6) Financial Considerations; (7) Alcohol Consumption; (8) Drug Involvement; (9) Psychological Conditions; (10) Criminal Conduct; (11) Handling Protected Information; (12) Outside Activities; and (13) Use of Information Technology Systems.

Who conducts the background investigations?

The vast majority (95 percent) of background investigations are conducted by the National Background Investigations Bureau (NBIB). Additionally, at least 21 federal agencies have delegated or statutory authority to conduct all or some of their own investigations. The Federal Bureau of Investigation (FBI), the U.S. Marshals Service (USMS), and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) have authority to conduct security clearance background investigations of certain categories of contractor positions. The Central Intelligence Agency (CIA) also has authority to conduct its own security clearance background investigations.

What happens during the background investigation?

According to the NBIB, during the investigation an Investigations Service Provider may conduct searches at police departments, sheriff’s offices, courts, creditors, and other record repositories. The individual’s friends, co-workers, landlords, family, and neighbors may be contacted to verify where they lived, worked, or went to school. Additionally, an investigator may interview the person to verify, expand upon, and/or clarify the information that was provided on their investigative questionnaire.

Do the President, Vice President, and Members of Congress need a security clearance to access classified information?

No. The requirements for the position of President, Vice President, Members of Congress, Supreme Court Justices, and other constitutional officers are outlined in the U.S. Constitution, and except by constitutional amendment, no additional criteria (e.g., holding a security clearance) may be required.

Can the President decide who on his staff can access classified information?

Yes. In his role as Commander-in-Chief, the President has the authority to establish the standards for access to classified national security information. President Trump has the power to decide that even people who are ineligible for a security clearance may be given access to classified materials.

What types of national security information can be considered for classification?

Government information can only be considered for classification if its unauthorized disclosure could reasonably be expected to cause identifiable or describable damage to the national security, and when it pertains to one or more of the following categories:

(a) military plans, weapons systems, or operations;

(b) foreign government information;

(c) intelligence activities (including covert action), intelligence sources or methods, or cryptology;

(d) foreign relations or foreign activities of the United States, including confidential sources;

(e) scientific, technological, or economic matters relating to the national security;

(f) United States Government programs for safeguarding nuclear materials or facilities;

(g) vulnerabilities or capabilities of systems, installations, infrastructures, projects, plans, or protection services relating to the national security; or

(h) the development, production, or use of weapons of mass destruction.

How many people have security clearances?

According to 2015 Annual Report on Security Clearance Determinations, approximately 4.3 million individuals held security clearances (of any level), including 2,885,570 security clearances at the Confidential or Secret level and 1,363,483 security clearances at the Top Secret level.

Joe Carter is an adjunct professor of journalism at Patrick Henry College, an editor for several organizations, and the author of the NIV Lifehacks Bible.

Photo Credit: President Donald Trump talks with German Chancellor Angela Merkel on Friday, March 17, 2017, in the outer Oval Office, joined by Senior White House Advisor Jared Kushner and Ivanka Trump. Official White House Photo by Shealah Craighead.