Go to *Website > Configuration > Settings > Shop - Products > Shop Product
Loading* and pick how the listing loads its pages. The setting is **per
website**:

* **Infinite scroll** (default): the next page is appended when the visitor
  reaches the bottom of the listing. A *Load more products* button shows up as
  a fallback if a request fails or if the browser has no
  ``IntersectionObserver``.
* **Load more button**: the next page is appended when the visitor clicks the
  button. This is the friendlier option for keyboard and screen reader users,
  and it keeps the footer reachable.
* **Pager (standard)**: turns the module off and leaves the standard
  ``website_sale`` pager alone.

The number of products of each page is **not** configured here: it is the
*Products per page* of the shop layout (open ``/shop`` as editor, *Edit* and
use the *Products Page* options), the same value the standard pager uses.