What Is It?
Google lets you purchase your place in the search results page based on what people are looking for. You choose a few words or phrases, along with how much you are willing to pay to be listed in the results. You only pay if people click the link to your site.
Why should I care?
It is often quite inexpensive, results are nearly instantaneous, and you only pay for results. Basically, Ad-Words makes you an advertiser on the internet, with your website being the product. Once people reach your site, it’s up to you to sell them on your services. Note that although this only applies to searches on Google, and that there are a large number of search engines, that Google does have the largest market share. You can also restrict your results to only show up for people in your geographic region so that you don’t pay for clicks where you have no interest in working.
How do I use Ad-Words
Full details on Ad-Words can be found here: http://adwords.google.com