The Google Keywords Tool also provides a picture of advertiser competition on a similar, relative scale. This is very useful in driving Pay per Click traffic to your website. The Google AdWords Keyword Tool can be a very useful starting step to help you select keywords for your campaign.
However, because you are not seeing any actual numbers, you cannot use the Google tool to predict search volume accurately. But it is an excellent resource for generating keyword lists as it is based on what terms people use to search on Google. And since it has the largest user base compared to all the other keyword research tools, you get a lot of depth when research keywords and building lists.