I wonder writing articles and posting it on article websites like ezeline etc, how can it help increasing the traffic ? Is there any other advantage for SEO for this ?

When you post articles on article directories like Ezine Articles, it not only increases targeted traffic but helps with SEO due to the high page rank of these directories. Pick 10 or 12 out with good page ranks, post articles to them often, and you will see after a few months that your site starts ranking higher. When you will submit Article to Article Directory there are option to put your website link in the author resource section you are allowed to put two links there by this you will get back link for your website. When some one will read your article they will click on your link which you already put author resource section they will redirected to your website by this you will gain targeted traffic