BEIJING, Feb. 6 -- U.S. President Donald Trump delivered his second State of the Union address on Tuesday. The following is an introduction to the annual speech.

The State of the Union Address is an annual message presented by the U.S. president to a joint session of the U.S. Congress, except in the first year of a new president's term.

Since 2011, the address has been given on a Tuesday. It includes a budget message and economic report of the nation, and also allows the president to outline the legislative agenda and national priorities.

The concept of a State of the Union address is enshrined in the U.S. Constitution, which states that the president "shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such measures as he shall judge necessary and expedient."

According to the National Archives, George Washington first gave his "annual message" to Congress on Jan. 8, 1790, in the Senate Chamber of Federal Hall in New York City, which was then the temporary seat of government.

The third president, Thomas Jefferson, discontinued the practice of delivering the address in person. Instead, the address was written and then sent to Congress. Jefferson set a precedent that lasted more than 100 years, until President Woodrow Wilson spoke in person to a joint session of Congress in 1913.

For many years, the speech was referred to as "the President's Annual Message to Congress." President Franklin Roosevelt was the first to call his speech the "State of the Union" address, according to the Senate Historical Office, and the term was made official under President Harry Truman.

Every member of Congress can bring one guest to the State of the Union address. The president may invite up to 24 guests with the First Lady in her box. The Speaker of the House may invite up to 24 guests in the Speaker's box. Seating for Congress on the main floor is by a first-in, first-served basis with no reservations. The Cabinet, Supreme Court justices, members of the Diplomatic Corps, and Joint Chiefs have reserved seating.

At least one member of the president's Cabinet is selected to stay behind from the speech each year in case of emergency. The designated survivor goes to a distant, secure and undisclosed location outside Washington while everyone else gathers to listen to the president's address in the Capitol.

The designated survivor must be eligible to be president. However, if a higher-ranking successor in the presidential line of succession survives a potential incident, the person would become president ahead of the designated survivor.