By default that continue shopping button on the cart page will take you back to the/one of the collection(s) of the item last added to the cart.
If there are no items in the cart, the continue shopping button will take you to the /collections-all page.
For those looking to change the link for the "continue shopping" button on the cart page, you can do so in the
cart__main.liquid file, depending on your theme. These files are found under Online store > Themes > Actions > Edit code > Sections.