Delivery is "real" when the speaker is honest and talks with the audience without acting.
Speakers may or may not be able to choose a delivery method, but keeping best speech practices in mind leads to success in each situation.
Your manuscript delivery method will vary depending on whether the manuscript is your own or someone else's.
It to your advantage to memorize your speech in some situations, and a distracting disadvantage in others.
An impromptu speech is given with little or no preparation, usually about a topic that the speaker knows well.
Extemporaneous, the most natural method of delivery, involves glancing at notes while maintaining crucial eye contact with the audience.
The key difference between a prepared and impromptu speech is the amount of time given to the speaker to rehearse and prepare.
An impromptu speech is given with little or no preparation, but the presenter is usually very knowledgeable about the subject matter.