Google Adwords are those little blue cubes you see plastered all over every web site from aardvarks.com to zygotefarming.org (just made those up).
Adwords can drive traffic to your site. However, you pay per click - PPC - so every time a Google user clicks on one of your blue cubes you get charged. This has led to rampant click fraud with competitor sites happily clicking away on your links, costing youmoney and depleting your marketing budget.
Google has been slow to react to click fraud since they receive their money whether it's a legit click or not so it's up to the PPC user to track for signs of click fraud.
Also, the cost per click is determined on a bidding system. Adwords users bid up the price of more popular keywords knowing that more Google users will see their ads. Clicks for the most popular keywords can reach $10 or more a click so you might want to use less popular keywords in your Adsense ads. You'll see less traffic but the per click cost will be lower.
The positives? Well, Google tracks costs and click throughs. That's always nice. But the best thing about Adwords is you only pay when a user actually makes a click that takes him/her to your site. No click, no cost, unlike banner ads and other paid advertising.
For those just starting out and operating on a "cookie-jar money" budget should use Adwords carefully and craft the text to intrigue the viewer. You have 60 characters to get your message across, including your URL. For this reason, it's often best to link to your site's home page rather than an interior page. It saves letters in your cube.
On the other hand, if you're directing visitors to a specific product page based on the keywords the Google user entered, the link should go directly to the product description and picture so the visitors don'thave to navigate through a bunch of tabs and fly-outs to find the exact product they're looking for.
Google (the verb) adwords to discover the prosand cons. There are site owners who have made lots of dough using this marketing tactic. There are also a lot of people who have lost it all through click fraud so you pays your money and takes your chances.
Finally, Adwords is great for simple A/B testing. Try one keyword, track your results and then try another and another until you have a golden list of keywords that actually produces results.
Like all on-line marketing, there's good and bad here, but if you keep track of your campaigns, you can quickly refine your marketing efforts to best effect.
Just keep you eye out for black hats who'll steal you blind by using click fraud. Not good, but easily preventable.