If SEO is the marathon, then AdWords is the sprint. Making updates to your web pages is great! but, to really see the benefit of your work, it may take a couple of months before you see noticeable changes in your rankings. That is where AdWords comes into play. Using Google AdWords to quickly boost your websites visibility, and traffic, can be a great way to quickly increase website traffic while you continuously work on your website's SEO.
AdWords is similar to SEO in the case that you don't want to just spam keywords and hope for the best. Spamming words that you think your consumers are searching for can result in your ads showing up in searches you are not trying to be in, and in the end that could end up costing you a lot of money, money you could be using to pay to be in the top position for terms you do want to rank for!
Constantly monitoring your ads is a great way to refine them, and pay exactly what you want for the best results. Listening to Google's recommendations on what keywords to add, and more importantly, what words to cut out, is a great way to refine your ads to perform the best that they can.