A blog can be a website and a website can be a blog.
A blog website has a page where only the site owner can enter and change the website content.
For a static site, like you might have now, only someone experienced in html, php, ftp, dns, jpg, gif, png can change the site pages.
This requires special software like Dreamweaver or Frontpage.
With a blog, if you can check your bank balance online, order stuff from Amazon, then you would be able to, at the very least, update the text on your website pages in the blog edit page.
In the blog you can create and edit pages & posts in a Microsoft Word style window.
On post pages, visitors are able to append ONLY POSITIVE comments to your web page. They cannot deface your site pages with bad comments.
Part of the work of keeping your site fresh and full of ‘hooks’ for Google to grab onto, is taken on by your site visitors.
Businesses that ‘get’ this get more hits than businesses that don’t.
In addition to this, blog sites have so many more built-in features, like SEO friendly urls, easy subscription links, etc., stuff I imagine may mean nothing to you, but means a lot to Google.
Take a look at information about the benefits of having a blog website in the links on the left.