Many PPC managers do not even know that such functionality exists. Seriously. They spend the budget in vain, and then shrug their shoulders, they say, “ I set everything up correctly, I don't know where your sales growth is”.
What are negative keywords for?
Let's turn to our tea topic again. Imagine that you sell tea only in Chisinau. You will often come across requests "buy tea in Balti", "buy tea in Soroca", etc. Stop words are used for these: just add “Balti” to the list of stop words, and no more request related to Balti will display your ads. This can actually save 50% of the budget, because every click costs money, and such irrelevant clicks will not bring profit.
The client deals with soundproofing apartments and everything related to this, but does not deal with soundproofing cars. On the day of inquiries about car noise isolation, there were about 50. After the work on identifying and cleaning negative keywords, the display of client's ads for such irrelevant queries was reduced to “very rarely, almost never”. Here's what the list of negative keywords looks like (and this is only 1%, in fact, it is many times larger):