A speech and a presentation are two very different things. If you've been asked to give one or the other, it is very important to understand the difference before you begin to prepare for your time in the spotlight. This helps you properly convey the necessary information to your audience.
The audience present for a speech tends to be very large, as the topic of the speech usually interests a large number of people. The audience for a presentation is typically much smaller. Presentations are usually applicable to only a small group of people.
Level of Formality
A speech is typically much more formal than a presentation. A person giving a speech likely wears a suit or a tuxedo, carefully planning each detail of his outfit. When someone gives a presentation, he usually dresses the same as he always does for work. When preparing for a speech, a person typically spends a great deal of time preparing a script, whereas someone giving a presentation simply notes a few talking points to discuss.
Visual aides such as slide shows containing charts and graphs are not used in speeches. Instead of using this visual assistance to convey the message of the speech to the audience, the speaker relies on his own voice, facial expressions, and overall emotions to make a point. In a presentation, a person might give the audience handouts containing the information he plans to discuss, or create a PowerPoint presentation to display facts and statistics.
A speech generally covers a very broad spectrum of ideas. For example; a CEO might give a speech to all employees about the current state of the company. He may provide high-level thoughts on a wide range of issues including company growth, profits and achievements. A presentation covers more specific topics. For example; a sales manager might give her boss a presentation showing her month end sales figures for each month, at the end of the year.