Blogging is technically an offshoot of content marketing. It is also separated from it here especially because it can be added as a standalone module for brands that wish to focus on long-tail keywords and supporting their main services.
Blogs are most certainly not new, they have been around for years. How they are used however, has evolved quite a bit.
Blogs are fantastic ways to grow your brand presence on a shoestring budget. Blog posts are usually much more design lean in comparison to pages, and as such are also much more affordable. That being said a blog can have every bit as much SEO benefit as a page has.
For every main service or product you provide, you should also have a web of blog posts supporting that service or product. This method introduces semantic terms that prop up your relevancy and visibility in search engine rankings.