There are many situations where you might need public speaking skills. It ranges from job presentations, sales pitches, sharing a story with some people and even for class presentations. The feelings that someone can experience before a public speaking situation can range from slight anxiety, shaky hands, quavering voice, but can also reach some extreme levels with intense anxiety, racing heartbeats, shortness of breath and even vomiting in some rare cases
The natural response of the human body for threats and dangers in order to survive is the fight or flight response where adrenaline will increase. This leads to an increase in heart rate, increasing the availability of oxygen in the blood. It will also be associated with quickening of thoughts and increased focus on the possible threat and the potential paths to escape. The fight or flight response can be beneficial in real threat situations. But for many it can be the same response for a public speaking event.
Understanding the topic that you want to present or speak about can highly reduce the chances of feeling public speaking anxiety. The more you know about the topic, the less likely you get lost. But even if you lose track, it would be much easier to recover. Practicing the presentation a few times, or recording a video of your mock presentation can also reduce the chances of getting lost at the presentation time.
Focusing your attention on the presentation material itself rather than the audience is also beneficial. Because typically the more the audience is more focused on the information you are presenting, and not actually the way you present it.