You don't have to select a choice in each drop down option, but you'll get more exact matches if you do.

 

So, if you're looking for an easy walk around Dunkeld, just select "easy - walking - Dunkeld and Birnam" from the drop downs.  If you want to browse through dozens of paths to walk or ride throughout the area, just choose "All Highland Perthshire" and leave the other choices clear.