I have played the piano since I was 3. Its an acoustic stringed instrument where the strings are hit by hammers.
Oh wow, I would love to play the piano, what are some of the top brands ?
Possibly the most famous is Steinway & Sons. Also the term piano is a shortened form of the italian word "pianoforte" which actually means "soft" and "loud" respectively.
When was the piano invented ? and by whom?
It was invented around the year 1700 by Bartolomeo Cristofori.
How long do people have to study to become semi-proficient with the piano ?
It took me almost 10 years to get good. I guess it depends on the person. 
Have you ever had a public performance ?
Yes, and the harder I hit the keys they harder the force of velocity which makes the soud louder for the audience.