In public speaking there are five important questions, which are often expressed as "who is saying what to whom, using which medium, with what effects?"
Good speakers are often able to change the way the listeners feel, and not just give them information. Public speaking can be a powerful tool to use for goals such as motivation, influence, persuasion, informing, translation, or simply entertainment.
The Ancient Greeks called public speaking rhetoric; the Romans called it oratory; it is also known as forensic speaking, or forensics. Propaganda is another name for speech in favour or against some point of view.