2. Which are a difference keyword suggestion tools

1.Google AdWords

Google AdWords is by far the best keyword suggestion tool.

You can get the search volume trends, keyword search volume, cost and ad positioning estimates & possible negative keywords. You also get to know the advertiser’s competition using which you can choose the less competitive keywords.

Though there are many keyword suggestion tools available, Google AdWords is the best opinion.

Google AdWords are Free Tools

https://adwords.google.com/select/KeywordToolExternal


2.Wordtracker

Wordtracker is a good keyword suggestion tool which actually is a paid one.
But now they have a free version. The free version is not bad.

Wordtracker gets you the past month search results.

The difference between Overture and Wordtracker is that, Overture shows the monthly searches for a particular keyword. Wordtracker shows the estimated searches made in a single day for a keyword.

http://freekeywords.wordtracker.com/


3.Overture

Overture is a keyword suggestion tool that shows the results of number of searches made for a keyword the previous month.

Though they say previous month, it has stopped showing stats after January. If you have any plans to know or target the search terms that were searched more in January 2007, then you can go for this tool. Or if you want a second opinion, then you can use this keyword suggestion tool.

Overture is a Free Tools

http://sem.smallbusiness.yahoo.com/searchenginemarketing/