††††An amplifier makes a sound louder or an electrical signal stronger.
The first amplifier came from the discovery of the vacuum tube. Although Thomas Edison had established the principles behind the tube, he didn't see a use for it.
The vacuum tube was eventually patented by Englishman John Ambrose Fleming, and in 1907 Lee De Forest and R. von Leiben implemented modifications which enabled it to amplify electrical signals. One of its first, and most important uses, was in the development of long-distance telephone links.
An amplifier can take an input signal and increase its strength when outputting it. The original signal remains identical apart from a change in magnitude. A good example of this would be a tape player which takes signals from a tape and converts them into high volume sound, otherwise the same as the original.
