PROVIDENCE, R.I. (WPRI) – President Trump has made headlines and triggered protests since taking office by issuing a number of what are known as “executive orders,” on topics ranging from immigration and refugees to Obamacare and regulations.

Here’s a quick explainer to get you up to speed on executive orders.So what exactly is an executive order?

Put simply, an executive order is a document issued by the president providing instructions to the agencies he runs, often on how a policy should be implemented. If – and it’s an important “if” – the executive order is consistent with the Constitution and the laws passed by Congress, it is a legally binding document.

Kenneth Mayer, a law professor and expert on executive orders, defines them this way: “An executive order is a presidential directive that requires or authorizes some action within the executive branch.”

Mayer continues: “Presidents have used executive orders to establish policy, reorganize executive branch agencies, alter administrative and regulatory processes, affect how legislation is interpreted and implemented, and take whatever action is permitted within the boundaries of their constitutional or statutory authority.”

Executive orders are also a way for presidents to show they’re making progress on key priorities and to send a message, even if members of Congress disagree (or are just moving slowly).Are there limits to what a president can do through an executive order?

Yes. A president cannot establish a new law or appropriate new tax dollars through an executive order – only Congress is allowed to do that. To be legal, an executive order must only explain how to carry out administration policy within the limits of the law.

A good example would be President Trump’s executive order last week involving construction of a new border wall. President Trump can’t actually just sign an order and therefore the wall will get built – Congress first needs to appropriate the billions of dollars it will cost. But Trump can tell his subordinates to take steps in their work to start to plan for the construction of a wall.

Another example – President Obama’s early executive order to close down the military prison at Guantanamo Bay. Obama ran into congressional resistance, and the prison never closed, despite what his order said.

The tricky part, of course, is determining where “explaining how to enforce a law” ends and “establishing a new law” begins. Obviously, a president will usually want to read the language of a law passed by Congress as broadly as possible, giving him maximum flexibility and authority. Others, however, may argue an executive order is too broad and the president is overstepping his authority.Can executive orders be overturned or reversed?

Yes. An executive order can be challenged in court, and a judge can decide that a president has overstepped his authority by issuing an overly broad executive order; this happened with President Obama’s second-term immigration enforcement changes.

Congress can also pass a bill that overturns an executive order, but the president has the power to veto the bill rather than let it become law (and if Congress is controlled by the president’s party, lawmakers may not want to rebuke him so frontally).

New presidents can also rescind executive orders issued by previous presidents, and often do. So it’s much easier to reverse an executive order than repeal a law passed by Congress, which means policies set out in executive orders are much easier to change.

And finally, the president who issues an executive order is free to rescind or amend his own order at any time.Are executive orders a new thing?

Nope. They’ve been around since George Washington, and some of the most famous (or infamous) policies in American history have been accomplished through executive orders. That includes President Lincoln’s Emancipation Proclamation freeing the slaves during the Civil War and President Franklin Roosevelt’s order interning Japanese-Americans during World War II.

Here’s an infographic put together by the Pew Research Center that shows how many executive orders presidents have issued:

(Executive orders aren’t just for presidents, either. Rhode Island Gov. Gina Raimondo and Providence Mayor Jorge Elorza both issue them, too.)Why are executive orders so controversial?

When executive orders are controversial, it’s usually because of their subject matter. Some of President Trump’s recent executive orders – on refugees, illegal immigration, the border wall, Obamacare – have touched on the most hot-button issues in politics, so it’s natural they have set off a firestorm. The same was true with President Obama’s executive orders on immigration, for instance.

They’re also controversial for the reason mentioned above – there is always a debate about how far a president can go in an executive order before overstepping the authority granted to him by the Constitution and Congress. Senate Majority Leader Mitch McConnell, R-Kentucky, alluded to that over the weekend in an interview about the refugee order: “The courts are going to determine whether this is too broad,” he said.

Not all executive orders are controversial, though. You probably didn’t see a lot of news reports about the order President Obama issued in 2015 making Christmas Eve a half-day for federal workers, for instance.Where can I learn more about executive orders?

The National Constitution Center has more information here.

And if you want to read the actual texts of the executive orders, the Trump administration is posting them here. (Previous presidents’ executive orders are here.)