For the purpose of this answer, I am assuming that an essay is written down on paper, and a presentation is given live by a person in front of an audience. I need to specify that because I don't want somebody thinking that this answer is going to compare a PowerPoint or Google Slides presentation to an essay.
A key difference has already been stated. A presentation is done in front of an audience. That audience might be classroom peers, a group of board members, or an audience at a conference. A presentation is given verbally; therefore, it presents information in an auditory format. A presentation will also convey information visually as well. This is completely unavoidable because things like kinesics, eye contact, platform movement, and gestures are all being taken in and analyzed by an audience. Non-verbal communication is key in a presentation. If the information is brilliant and earth-shattering, but the presenter looks bored and is dressed like a vagrant, the presentation may not be well received. All of those non-verbals are critical to a presentation. Word choice, organization, and transitions are also critical.
In an essay, most of the focus is on the organization, diction, and flow of the words on the page. Formal writing grammar is now very important, though it need not be advanced. Tone is also important in an essay, but it is much harder to implement because it must be done through the writer's word choice. In a presentation, tone can be conveyed through word choice, volume, gestures, eye contact, and other things.
Finally, a few similarities. Both formats are designed to convey information. Both formats can be very effective, and both formats can be incredibly difficult to master.