This is a list of some product, like books or video games, that shows what book or video game is selling the most copies.

For instance the NY Times runs a Best Sellers list.
So does Amazon.com.

Diffrent retail outlets like to get togeather on the top selling vgc and computer games for a list. (Which unfortunately put's several million one dollar copies of Deer Hunter at #1, most of the time, hence proving it's marketing, not quality, that makes a best seller.)

There are also often Best Seller Lists of movies, which aren't called Best Seller Lists, because they are selling viewings via tickets, which explains why it's called "The top movies at the box office."