Sometimes, we're being asked in support:
How do I re-order products on the Catalog page?
To be able to sort the products shown on the Catalog page, you will need to create a collection that uses the same handle, ie. 'all', as the automatic collection Shopify created for that URL (/collections/all).
Here are the steps:
Go to your Collections page in your admin.
Create a smart collection with title 'All' and the condition 'product price is greater than 0'. Save.
On that same page - the admin page of your new collection, pick the 'Manually' option in the Reorder this collection drop-down, then reorder the products using the small drag and drop handles. Alternatively, use an automatic sorting criteria such as 'By Best Selling'.
The products shown at /collections/all should reflect your changes.
If you do not like the title 'All' that shows up on the /collections/all page, and only after having completed steps 1 to 4, go back to your All collection admin page, click on the Edit link for it, and change the title to whatever you like better, then save.