President Donald Trump has used his first 100 days in office to take a number of executive actions. He has issued 30 executive orders and 28 presidential memoranda as of April 28, 2017, according to the White House website.

To help understand what these mean, here is a breakdown of what executive actions are and what orders Trump has made.

What is an executive order?

Executive orders are a type of executive action that have the force of law and are used to bypass Congress to direct government officials or agencies. There is no direct language in the Constitution that allows the president to issue executive orders, but Article II, where it grants the president “executive power,” is often cited as why they are permitted. 

Congress cannot overturn executive orders. It can try to pass bills that would make it more difficult for the order to be implemented, but the president always has the option to veto the bill. The orders are subject to judicial review and can be overturned by the Supreme Court. 

Presidential memoranda and proclamations are other examples of executive actions the president can take, but they all have “similar purposes,” says Columbia University political science professor Robert Shapiro. Executive action also includes decisions the president makes as the commander-in-chief and in dealings with foreign governments.

Orders are the only actions required to be numbered and published in the Federal Register, but memoranda may also be recorded in the register. Both, along with proclamations, are recorded on the White House website

The difference between orders and memoranda is the most unclear. Former President Barack Obama often said he issued orders at a lower rate than presidents in the last 100 years, but if his memoranda are added to his orders, the rate is much higher. Legally, there is little difference between the two. 

Trump has issued both orders and memoranda in his first months in the Oval Office. Here’s a look at his major actions:

Accountability at the Department of Veterans Affairs

The president signed an order on April 27, 2017 to establish a VA Office of Accountability and Whistleblower Protection and appoint an individual as the director of the office. 

"Buy American and hire American"

The president issued an order on April 18, 2017 declaring the administrations position to buy and hire American. He called for the heads of agencies to review their departments to ensure that they are promoting the hiring of Americans over immigrants and buying products made in the United States over other countries.

Undoing Obama’s climate change regulations

Trump signed an executive order, The “Energy Independence” order, on March 28, 2017, that will undo some of the regulations Obama put in place to combat climate change. The main target is the Clean Power Plan, which requires states to reduce carbon emissions from power plants. The order will also reverse a ban on coal leasing on federal lands and undo rules to curb methane emissions from oil and gas production.

Revised temporary travel ban*

Trump signed a revised version of his original executive order, barring citizens from six Muslim-majority countries from entering the United States for 90 days, on March 6, 2017. Among other changes, the new order excludes Iraq from the list of countries included in the temporary travel ban.

*The order's execution was blocked by a Hawaii judge on the Court of Appeals for the Ninth Circuit.

Cutting federal regulations

Trump took steps to reduce the number of regulations in the federal government when he signed an executive order on Feb. 24, 2017. The order instructs federal agencies to establish task forces that will focus on regulatory reform. The president said each task force will have to offer recommendations on which regulations to repeal or simplify.

Dodd-Frank Law review

An executive order signed by Trump on Feb. 3, 2017, called for a review of the 2010 Dodd-Frank Wall Street reform regulations that were put in place to prevent a repeat of the 2007-2008 financial crisis. The order is largely symbolic, as Congress must approve any changes to the legislation.

Lobbying ban

Trump signed an order on Jan. 28, 2017, that bars members of the administration from lobbying their own agency for five years after they leave office. The order also says administration members cannot lobby government appointees for two years.

ISIS plan

This memorandum, signed on Jan. 28, 2017, directs the president's Joint Chiefs of Staff to provide a plan, within the next 30 days, to defeat ISIS. In addition, Trump signed a memorandum that calls for reorganizing the National Security Council and Homeland Security Council.

Temporary ban on refugees*

The president signed an executive order on Jan. 27, 2017, that will suspend U.S. entry for all refugees for 120 days and suspends the Syrian refugee program until further notice. The order, which Trump said will "keep radical Islamic terrorists out of the United States of America," also limits entry for at least 90 days from Syria, Iran, Sudan, Libya, Somalia, Yemen and Iraq.

*The order's execution was blocked in court and a revised version was signed by Trump on March 6, 2017. The revised travel ban was also blocked in court before it could be put into place.

Military readiness

During a ceremony at the Pentagon, Trump also signed a memorandum to beef up the U.S. military. The administration will develop "a plan for new planes, new ships, new resources and new tools for our men and women in uniform," Trump said on Jan. 27, 2017.

Building the U.S.-Mexico border wall

Trump signed an executive order on Jan. 25, 2017, to start construction of a wall along the nation's border with Mexico, fulfilling a campaign promise. In an interview with ABC News, the president said planning for the wall started immediately and construction could begin within months.

Sanctuary states/cities funding

The president also signed an executive order on Jan. 25, 2017, that strips federal grant money from "sanctuary" states and cities that harbor illegal immigrants and often refuse to cooperate with federal authorities.

Keystone XL and Dakota Access pipelines

Trump signed two presidential memoranda on Jan. 24, 2017, to move ahead with plans for the Keystone XL and Dakota Access pipelines.

He also signed an order "to streamline and expedite, in a manner consistent with law, environmental reviews and approvals for all infrastructure projects."

Trans-Pacific Partnership

The president withdrew the United States from the 12-nation Trans-Pacific Partnership with a presidential memorandum on Jan. 23, 2017. 

Mexico City Policy

Trump restored the so-called Mexico City Policy, which Obama had revoked in 2009. The policy prohibits federal funding for international organizations that promote or provide abortions. 

Federal hiring freeze

Trump issued a hiring freeze for the executive branch in a memorandum on Jan. 23, 2017. It does not include the military.

Affordable Care Act

On his first day in office, Trump signed an order instructing federal agencies to ease regulations associated with the Affordable Care Act, Obama’s signature health care law. It called for agencies “to waive, defer, grant exemptions from, or delay the implementation of any provision or requirement of the Act that would impose a fiscal burden.” But its impact is not entirely clear, Shapiro said.

“It’s symbolic at the moment,” Shapiro said of the order. Essentially, it gave Trump and his secretary of health and human resources, Tom Price, discretion where the law allows, but changes to the policy will need to be passed by Congress.

What happens to an executive order when a president’s term is over?

Executive orders don’t expire when a president’s term is over, but a new president can issue an executive order to override the previous executive order. This is what Trump has done to some of Obama’s executive orders.

How many executive orders do presidents issue?

Obama issued 277 executive orders in his eight years as president, according to the American Presidency Project, which has tallies of executive orders issued by every president. 

The president with the most executive orders was Franklin D. Roosevelt. He issued 3,721 executive orders during his three terms.

The data, however, does not include presidential memoranda, which makes it difficult to access a president’s overall use of executive actions.