Code-Pega-List is a class. When you use a list type page in your code, the class of that page should be Code-Pega-List. Suppose you are using a page which holds list of products. Then in Page And Classes tab declare the page with class Code-Pega-List. While using each element use syntax ProductList.pxResults(i) to access individual page of that list. pxResults is a Page List type property of Code-Pega-List class.
Code-Pega-List class will be used as the class for all PageList type pages you will be using. As this is a class, you can store different values in the instance of the class. This is the concept of list. This is a list of elements. Each element can be accessed using .pxResults. Like all other list, there is a count of element and that is what pxResultCount is. If you have pxResults the pxResultCount will also be populated.