Public speaking involves structuring a speech to inform, influence, or entertain an audience. There are five basic elements: the speaker, message, audience, medium, and effects. There are four main types of public speaking: informative, persuasive, ceremonial, and extemporaneous. An informative speech aims to impart information to the audience. A persuasive speech attempts to influence and change opinions. A ceremonial speech is given at special occasions. An extemporaneous or impromptu speech requires quickly organizing thoughts on a topic. Effective public speaking requires understanding the audience and researching their needs and interests. The style and delivery of the speech should also engage the audience.