I have been taking piano lessons since I was 5.
I have never played the piano although I am familiar with how one uses a keyboard with keys to cause the hammers to strike the strings and produce sound.
How do the strings make all the different sounds?
The Italian term "piano" refers to the variations in volume produced by the pianist's touch or pressure.
That's interesting I never knew that. When were pianos invented? 
Pianos were invented around the year 1700.