A presentation usually has visual aids. A speech is more reliant on the spoken word. When you give a speech, you are talking to your audience and they are listening. When you give a presentation, your audience is usually learning something from you and you want them to take some kind of action.
A speech is an event where a speaker stands before a group of listeners and transmits information by no other means than speaking to the group. The audience listens passively and may or may not be invited to ask questions at the conclusion of the speech.
A presentation may or may not include a speech. During a presentation, the speaker uses additional media to transmit information to the audience. These media may include visual aids such as PowerPoint or handouts, video clips, audio clips, and other items. The presentation may or may not include audience participation, and questions may occur during or following the presentation..
The main differences really boils down to the connotations of the words themselves. Speech is defined by Merriam-Webster as "something that is spoken,a usually public discourse."A speech is a type of oral recitation, whether from memory or notes. It is a way to communicate ideas auditorily to an audience, with a specific purpose in mind.
Presentation, on the other hand, is usually refered to as a more interactive experience. Salesmen present their sales pitch, showing the item being sold, demonstrating its good qualities, and letting the consumer ask questions. Presentations are about giving the information in a way that appeals to the audience, rather than necessarily speaking the information.
There is really one clear and real difference between speech and presentations. Speeches contain only spoken words. In contract presentation include other methods of conveying information such as flip-charts, slides, power point presentations, videos, physical models and even demonstrations. All other differences between either result from this primary difference or is more a difference in usage of language.
On some occasions presentation are more suited and on others speeches are more suited. For example, when a lot of factual data and analysis is to be conveyed, the additional aids of presentation are very useful, but when the speakers intends to appeal to emotions of the audience only verbal speeches are more effective. For this reasons presentations may be used more frequently when cold logic and data is involved. In other situations speeches are used more often. Because of this some people also differentiate between speech and presentation based on occasion and the subject matter. However, it is worth while noting that in certain type of situations the word presentation is more common irrespective of the format for presenting information used. For example, scholars always make presentation at seminars, even if it consists wholly of words spoken by them, and politicians always give speeches at election rallies, even when they use some presentation aids.