To make your advert a success on Google Adwords, keywords are fundamental. Discovering what works and what doesn’t work for your advert is all part of the learning process.
You could find that your ad is generating 1000’s of impressions on a broad match keyword (fantastic), yet is failing to generate any clicks (dreadful).
Such a nightmare situation is probably due to the fact that your keyword has no relevance to the search query whatsoever, but appears time and time again because Google Adwords thinks it does.
Therefore it is important to tell Google Adwords of the words that are not relevant to your keywords. These are known as negative keywords.
Spending a lot of time working out what your negative keywords are is essential, so that Google Adwords does not misconstrue what is relevant.