A speaker can be defined as an electronic output device that is typically used for the conversion of an electromagnetic wave to sound wave.
Basically, this conversion is done through the help of a hardware electronic component known as transducers.
The main purpose of a speaker is to produce an audio output and as such avail the computer users an ability to hear or listen to sounds.
In this scenario, you decide to test an audio clip that you have inserted into your presentation, but before you do that you make sure that the computer has a speaker because speakers are typically used for the production of audio output (sounds).
