Public speaking, also called oratory or oration, has traditionally meant the act of speaking face-to-face to a live audience. Today it includes any form of speaking (formally and informally) to an audience, including pre-recorded speech delivered over great distances by means of technology.
Confucius, one of many scholars associated with public speaking, once taught that if a speech was considered to be a good speech, it would impact the individuals' lives whether they listened to it directly or not. His idea was that the words and actions of someone of power can influence the world.
Public speaking is used for many different purposes, but usually as some mixture of teaching, persuasion, or entertaining. Each of these calls upon slightly different approaches and techniques.
Public speaking was developed as a primary sphere of knowledge in Greece and Rome, where prominent thinkers codified it as a central part of rhetoric. Today, the art of public speaking has been transformed by newly available technology such as videoconferencing, multimedia presentations, and other nontraditional forms.