President Barack Obama released this week an executive order on tougher gun control measures after years of pleading with Congress to make it harder for certain people to purchase and sell firearms. He was scheduled Thursday night to hold a town hall meeting in Virginia to talk about his plan to establish an expansion of background checks for firearm purchases and stronger reporting requirements for stolen or missing guns.

"We're going to require firearms dealers to report more lost or stolen guns on a timely basis," Obama said Tuesday during a statement from the White House. He alluded to a December mass shooting in California, adding, "Even after San Bernardino, they've [Congress] refused to make it harder for terror suspects who can't get on a plane to buy semi-automatic weapons."

Obama has been accused of sidestepping the Constitution to change federal law without Congress' approval. But the White House says he has the legal authority to do so. So what exactly is an executive order, and when do Obama's gun control measures go into effect?

"Executive orders are generally used to direct federal agencies and officials in their execution of congressionally established laws or policies. However, in many instances, they have been used to guide agencies in directions contrary to congressional intent," explained. Executive orders don't require congressional approval under Article II of the U.S. Constitution, which defines presidential powers.

It's unclear when all the new requirements in Obama's order will take effect, though the changes are immediate. The Bureau of Alcohol, Tobacco, Firearms and Explosives is still finalizing a rule to require background checks for people trying to buy the most dangerous weapons and other items through a trust, corporation or other legal entity, among other changes, the White House has said. Meanwhile, some critics have said the gun control plan is largely political theater that will do little to stop illegal gun sales, mass shootings or other gun-related problems.

Obama has issued executive orders before, such as one late last year that gave federal employees a half-day off on Dec. 24, and the June policy that removed the threat of criminal prosecution for U.S. families who negotiate with kidnappers when their loved ones are taken hostage.

George Washington passed the first executive order on April 22, 1793. The policy required the prosecution of any citizens interfering with the war between England and France. In a move that divided the nation, Dwight Eisenhower's order authorized U.S. troops to enforce the integration of public schools in Arkansas in 1957.

Franklin D. Roosevelt issued the most executive orders, with a total of 3,721, or more than 307 for each year he was in office.