Google Adwords is a very powerful marketing tool if used correctly. Many people think that they can set up an Adwords campaign and run it effectively, but unless you understand all the options and set them correctly then you can be wasting money, seeing little return.
One thing that Adwords does is give each of your keywords a score out of ten. This is made up of three parts, Ad Relevancy, expected click through rate and landing page experience. This score is known as the quality score and the higher it is the cheaper it will be for you to compete for that specific keyword.
If you find that your ad relevancy score is below average then you need to re-read your advert and make sure that it is as relevant as possible to the keyword you are bidding on. If you need to improve it you may wish to remove it from the current ad group and put it in one of its own where you can write a new ad that is highly relevant.