There are 2 different types of collection pages.
A collection page with a list type can be used with pagination and group by. For example if you have a blog collection with 500 blog posts you wouldn't show them all on 1 page as that would load very slowly. Instead you use pagination and only show 10 items per page and Versoly will create 50 dynamic pages based on the content. Group by filters dynamic content by another collection, for example you want a page that only shows blog posts with a certain category. Pagination and group by can be combined if you have lots of blog posts with the same category
Whereas a details page is used with individual items. For example if you have 500 blog posts Versoly will create 500 dynamic pages using that content.