ChatGPT Prompt: As a motivational speaker, please provide a detailed response on the art and science of public speaking, including the different types of speeches and their purposes. Please explain how to structure a speech for maximum impact and how to deliver it effectively, including the use of body language and vocal techniques. It would also be helpful to provide guidance on how to find speaking opportunities and how to build a personal brand as a motivational speaker. Additionally, please address common challenges that arise during the speaking process, such as stage fright and engaging the audience, and how to overcome them. Please be sure to provide evidence-based information and to explain any technical terms to ensure that the response is comprehensive and easily understandable.