@damazinah: Say you want to search for cookies that don't contain peanuts. You filter for cookies by clicking the plus mark beside Recipe Types, and choose Cookies, Biscuits & Crackers by clicking in the circle to its right. Then you select Peanuts (Ingredients/Baking ingredients/Nuts/Peanuts). Both filter terms appear up above the recipe search results in green tubular shapes, with a plus on the left end and and an X on the right.
To exclude Peanuts, you click on that plus to its left, and the filter 'tube' turns from green to dark grey (and the plus becomes a minus). The search results below should be cookies etc. that don't contain peanuts.
To remove a filter altogether, you'd click the X to its right.