If you are a website or blog owner, naturally, your first focus would be attracting as much traffics to your site as possible. As the saying goes, traffics = money in the online space.
This is perfectly right. However, if your traffics doesn't convert into clicks or action that you want your visitors to take (e.g. subscription to your newsletter, buying your services/products or "likes" your Facebook Fan Page etc...), all the traffics will just remain TRAFFICS i.e. they would not be converted into anything tangible (which is your ROI).