We have set up a product catalogue, but now want to restrict it, for instance to make a catalogue of one category of products. Let us modify the catalogue we've just set. Alternatively, you can use a clone of it (In order to clone the catalogue, go to Structure → View; in the column "Operations" and the row of the view we've created, click on the small arrow and then on "Clone"). We just add yet a new filter criteria in the view, clicking on the "Add" button at the right of "Filter criteria".
Then we choose "Commerce Product: Tags (field_tags)" as criteria (We can search the term "tag" for this.).
 Tags (field_tags)" as filter criterium
Then we can choose "Dropdown" as "Selection type".
Choose "dropdown" in the filter configuration.
Then a crucial step is to choose, as "relationship", "Products referenced by field_product_reference", because the tag field is not in the product display, but in the product itself. Another option would be to put the tag on the Product display.
Select the relationship, and select terms from vocabulary "Tags".
Optionally, we can now check the box "Expose this filter to visitors, to allow them to change it", so that our visitors be able to choose other categories of products.
Expose the filter and select terms from vocabulary "Tags" We also need to choose one or more terms from our vocabulary. Here, we xhoose "Earring".
After we have clicked on "Applied (all displays)", at the bottom of the page, we get our filtered catalogue, where we can choose ourselves the categories.
 only earrings
Don't forger to save your view (at the right top of the page).

Limitation

The vocabulary hierarchy doesn't work. In other words, if "earrings" is a sub-category of "jewellery", then choosing "jewellery" only shows the products tagged as "jewellery", but not those tagged as "earrings". The visitor has to choose both "jewellery" and all its sub-categories to get all these products. An alternative would be to put tags in the Product display, rather that using the tags of the products.