All products have been flagged with a lot of keywords. When you select something in the lefthand menu, it ends up as these grey "flags". Together they give you your selection.
You can select multiple options, for example, if you're not sure if you'd like to buy red sandals or ballerinas, you can select both 'Ballerinas' and 'Sandals' in the menu and narrow the selection down by clicking on the red square further down.
This example below will show products flagged with "boots", "black" and "size 37" meaning off course that the list contains all black boots in size 37! Easy right?
Try adding two colours or two sizes!
If you selection doesn’t get any results then try to remove a "flag" by clicking the red ⊗ symbol.