I want to change the representation of product page like add some new things, reviews at the end of the page and reposition some elements. In which and where in files, I have to change. I am finding all given answers confusing.
To send customer reviews in the end of page edit your catalog_product_view.xml at below location
And add this line of code there
<move element="reviews.tab" destination="main.content" after="-"/>
Keep cache disable or flush your cache.