A blog can help in SEO, when that happens visibility of your business will also improve. When your business's visibility improves, you will get sales. It is as simple as this. Likewise, you can also use your blog for promotion.I understand a blog can help in SEO for a business as a product listing does not have a lot of room for SEO implementation but blogging allows to do SEO through multiple strategies. But I am confused, how can it help in sales. I mean how will a blog help an ecommerce sites bring in sales.