We are more likely to show up in relevant search results if our tag words match those that the buyer uses to search with. Our tags should state what the item is and accurately describe it for being what it is.
For instance, if the item is earrings, tag words such as "pistachio" and "glass tile" do not accurately describe the item as being earrings. A search in the handmade category for "pistachio" yields 2,829 results, which include a mixture of dolls, baby booties, dog collars, sweaters, scarves, and all sorts of things. A search in the handmade category for "pistachio earrings" yields 320 results. While it's true that the search with the word "pistachio" gives far more results, the problem is that these results are not all relevant to pistachio colored earrings. The search for "pistacho earrings" gives far less results, but they are all relevant to pistachio colored earrings.
If I wanted a pair of pistachio colored earrings, I would not search with the tag word "pistachio", because I have no interest in looking through all the non-relevant things only to find pistachio colored earrings. Therefore, I would search with the words "pistachio earrings" so that I would get results for only what I am looking for. Same thing would happen if I searched for "green glass" instead of "green glass earrings". It's important for our tag words to state what the item is and accurately describe it for being what it is. The buyer will be very specific for what they search for and will use words which state what it is and which describe it (such as "green glass earrings", instead of "green", "glass", "earrings"). Because the buyer will be very specific about what they want and will use specific words, they will need to use phrases to search. If we use phrase tags which match those phrases the buyer uses, we will be far more likely to show up in the search results for things that are relevant to what they are looking for.