1) The President of the United States serves as the head of state and the head of government, responsible for leading the executive branch and representing the nation domestically and internationally.

2) The word "guitar" contains three vowels: U, A, and I.

3) The first graphical web browser, Mosaic, was released in 1993 and played a key role in popularizing the World Wide Web.

4) In Chinese mythology, the Dragon Boat Festival (also known as Duanwu Festival) is celebrated to honor Qu Yuan, a poet and statesman of ancient China. It involves dragon boat races, eating sticky rice dumplings (zongzi), and performing rituals to ward off evil spirits and protect against diseases.