This might seem like an odd question, but what do you mean by 'sound'?
Yes it is an odd question... Or is it?
I can immediately think of four scenarios where this question is perfectly valid.
Firstly, anyone who is totally deaf and has never experienced sound must indeed wonder what the sensation is like, and what sound is useful for.
I am not even going to attempt an answer to this as it probably could not be answered satisfactorily in 10,000 words, let alone a couple of paragraphs.
Let's move on to something more closely related to music production and sound engineering...
Sound traveling in air
Sound in this context is a wave motion that travels in air; the actual sound that we hear naturally.
Sound also travels through liquids and solids, but sound traveling in a liquid is only rarely of interest to us. Sound traveling through solids is very important in the context of soundproofing, even though we don't directly hear it in this medium.
One common point of confusion however is that sound does NOT travel through electrical wires. This is an electrical signal that represents sound. It would not be unusual to call it a sound signal however.
Sound vs. music
My third meaning for 'sound' is an interesting one. Musicians can produce sound using nothing more than acoustic instruments and voices. This is sound.
But broadcasting organizations, theatres and other enterprises often have a Sound Department and a Head of Sound. But they don't make music, they work with microphones, mixing consoles, amplifiers etc.
In this context therefore, 'sound' is short for 'sound engineering'.
The sound of a microphone, preamplifier or mixing console
Finally there is the use of the word 'sound' to mean the way a piece of audio equipment colors the actual sound or the signal it is handling. So a vintage tube microphone, for instance, has a 'sound' even when it is in its box. The engineer will choose it because he knows from experience that that particular microphone's sound will suit the instrument or voice he is about to record.
Microphone preamplifiers and mixing consoles also often have a 'sound'. The term 'sound' in this sense is only commonly used in connection with analog equipment. Digital equipment is hardly ever described as having a sound, unless the commentator is criticizing digital audio in general.
So, four meanings of the term 'sound'. It wasn't such an odd question after all.