A motivational speaker or inspirational speaker is a speaker who makes speeches intended to motivate or inspire an audience. Such speakers may attempt to challenge or transform their audiences.
Business entities may employ motivational speakers (for example) to communicate company strategy with clarity, to help employees to see the future in a positive light, or to inspire workers to pull together. The talk itself is often known as a pep talk.
Antiquity
Modern scholarship on classical oratory as a means of persuading and moving audiences can look to Cicero's De Oratore as an exemplar for "the rhetoric of motivation".
References
Motivational speaker Wikipedia(Text) CC BY-SA