Basic clarity on some magento default function

Question

I had gone through a interview process. They fired some questions below which I don't know answers and couldn't find in google. The questions are below.

1. How to create a object and why we need to create objects ?
2. What is use of EAV database structure ?
3. Why the plugin is used ?
4. What is the use of requireJS ?
5. Why magento uses knockout JS ?
6. What the generated/code folder containers ?
7. What means interceptors ?
8. Why we use reindex command ?
9. Why Js and css are compiled and saved in PUB folder what is the use of it ?
10. When We should use public,protected and private functions?