Many people use the words speech and presentation interchangeably.   Admittedly, I often do so myself.  But, there is a difference:  how we 'deliver' a speech is not the same way we 'give' a presentation.  A speech is more formal than a presentation; a speech is usually shorter than a presentation; and, according to Webster's Dictionary, a speech is a public discourse:  an address.  Define address and we have:  to deliver a formal speech.

Speeches are heard at weddings, funerals, inaugurations, dedications, commencements, graduations and in other formal situations in which the audience did not come to actually hear the speaker as much as they came to attend the special occasion.

On the other hand, Webster's defines a presentation as:  a descriptive or persuasive account.  The length of the presentation is varied.  If you are attending an all-day conference, the presentations may average 40-45 minutes; however in other situations, a presentation may be as brief as 20 minutes or as much as 90 minutes. 

If you are giving a sales presentation to one or two people, you may only speak for 5-10 minutes. 

Whereas speeches are part of an occasion, those who are in the audience to hear a presentation are most often in attendance just to hear the presentation. 

[Incidentally, before radio and TV, people actually did go to hear speeches.  And, they were long!  When the GettysburgCemetery was dedicated in November of 1863, President Lincoln was invited almost as an afterthought.  The featured speaker on the agenda was Edward Everett, one of the most famous orators of the 19th century; and, this former Harvard president spoke for two hours!]

A presentation often includes some form of visual aid.  It may be PowerPoint, slides, video, or even just a white board.  Whereas with a speech, you will most likely stand at a lectern, there is much more freedom with a presentation as far as body movement is concerned.   If you wish to stand at a lectern, you may do so if one is provided; however, you will find that many 'presenters' prefer the ability to move on the stage or at the head of the boardroom table or in the front of the meeting room.  

Both speeches and presentations may be either informative or persuasive.  These are the only two reasons for public speaking.  And, while both speeches and presentations are hopefully entertaining, I do not consider the comic after-dinner speaker in the same category as the person delivering a speech or making a presentation.  While there may be a great deal of humor in the speech or the presentation, they are essentially learning experiences.  Upon listening to a humorist, you may be entertained but you are probably not learning anything.

• Speeches are written out word for word; presentations are not.
• Speeches are read; presentations are not.
• If given properly, a speech will sound the same no matter how many times you deliver it.  A presentation will not.