Public speaking (also called oratory or oration) is the process or act of performing a speech to a live audience. This type of speech is deliberately structured with three general purposes: to inform, to persuade and to entertain. Public speaking is commonly understood as formal, face-to-face speaking of a single person to a group of listeners.
There are five basic elements of public speaking that are described in Lasswell's model of communication: the communicator, message, medium, audience and effect. In short, the speaker should be answering the question " who says what in which channel to whom with what effect ?"
Public speaking can serve the purpose of transmitting information, telling a story, motivating people to act or some combination of those. Public speaking can also take the form of a discourse community, in which the audience and speaker use discourse to achieve a common goal.
Public speaking for business and commercial events is often done by professionals. These speakers can be contracted independently, through representation by a speakers bureau, or by other means. Public speaking plays a large role in the professional world; in fact, it is believed that 70 percent of all jobs involve some form of public speaking.
Although there is evidence of public speech training in ancient Egypt,  the first known piece  on oratory, written over 2,000 years ago, came from ancient Greece. This work elaborated on principles drawn from the practices and experiences of ancient Greek orators. Aristotle was one of the first recorded teachers of oratory to use definitive rules and models. His emphasis on oratory lead to oration becoming an essential part of a liberal arts education during the Middle Ages and the Renaissance. The classical antiquity works written by the ancient Greeks capture the ways they taught and developed the art of public speaking thousands of years ago.
In classical Greece and Rome, rhetoric was the main component of composition and speech delivery, both of which were critical skills for citizens to use in public and private life. In ancient Greece, citizens spoke on their own behalf rather than having professionals, like modern lawyers, to speak for them. Any citizen who wished to succeed in court, in politics or in social life had to learn techniques of public speaking. Rhetorical tools were first taught by a group of rhetoric teachers called Sophists who are notable for teaching paying students how to speak effectively using the methods they developed.
Separately from the Sophists, Socrates, Plato and Aristotle all developed their own theories of public speaking and taught these principles to students who wanted to learn skills in rhetoric. Plato and Aristotle taught these principles in schools that they founded, The Academy and The Lyceum, respectively. Although Greece eventually lost political sovereignty, the Greek culture of training in public speaking was adopted almost identically by the Romans.
In the political rise of the Roman Republic, Roman orators copied and modified the ancient Greek techniques of public speaking. Instruction in rhetoric developed into a full curriculum, including instruction in grammar (study of the poets), preliminary exercises (progymnasmata), and preparation of public speeches (declamation) in both forensic and deliberative genres.
The Latin style of rhetoric was heavily influenced by Cicero and involved a strong emphasis on a broad education in all areas of humanistic study in the liberal arts, including philosophy. Other areas of study included the use of wit and humor, the appeal to the listener's emotions, and the use of digressions. Oratory in the Roman empire, though less central to political life than in the days of the Republic, remained significant in law and became a big form of entertainment. Famous orators became like celebrities in ancient Rome—very wealthy and prominent members of society.
The Latin style was the primary form of oration until the beginning of the 20th century. After World War II, however, the Latin style of oration began to gradually grow out of style as the trend of ornate speaking became seen as impractical. This cultural change likely had to do with the rise of the scientific method and the emphasis on a "plain" style of speaking and writing. Even formal oratory is much less ornate today than it was in the Classical Era.
Despite the shift in style, the best-known examples of strong public speaking are still studied years after their delivery. Among these examples are Pericles' Funeral Oration in 427 BCE addressing those that died during the Peloponnesian War; Abraham Lincoln's Gettysburg Address in 1863; Sojourner Truth's identification of racial issues in " Ain't I a Woman? ”; and Mahatma Gandhi's message of nonviolent resistance in India, which in turn inspired Martin Luther King, Jr.'s " I Have a Dream " speech at the Washington Monument in 1963.
While technology and methods used in public speaking have traditionally featured simple oratory structure, new speaking technologies have been created in the past few decades that have transformed traditional speaking. New advances in technology have made way for more sophisticated communication for speakers and public orators. Lecterns hold papers while speakers talk. A speaker can project his or her voice with the aid of a public address system or a microphone and loudspeaker when speaking in front of a large audience. Public speakers may also use audience response systems, allowing listeners to interact with the speech as it happens.
Today, the technological and media sources that assist the public-speaking atmosphere include both telecommunication and videoconferencing, which have revolutionized the way public speakers communicate to masses across the world. David M. Fetterman of Stanford University wrote in his 1997 article Videoconferencing over the Internet: "Videoconferencing technology allows geographically disparate parties to hear and see each other usually through satellite or telephone communication systems." This technology is helpful for large conference meetings and face-to-face communication between parties without demanding the inconvenience of travel.
The use of head-mounted displays such as Google Cardboard, a virtual reality platform which immerses users in a variety of realistic environments in which they can train according to each, is a new way to educate public speakers that helps them prepare for a range of possible situations.