Problem keywords waste budget. They are those irritating keywords in your campaign that cost too much, or aren’t converting well. Perhaps they are drawing lots of clicks but aren’t getting conversions. Or maybe the cost per click is high and the conversions are low. Either way, these little boogers can be an enormous detriment to a healthy Adwords campaign.
The great thing about pay-per-click advertising is that Google only charges you when your ad gets a click. Therefore, it is important to refine your Adwords campaign to maximize relevant, useful clicks that lead to conversions.
Refining your campaign also helps you avoid irrelevant clicks that waste your budget. Thus, weeding out your problem keywords is one way to hone your campaign and maximize quality clicks.