I honestly wouldn't know, but my best guess is it isn't an API, it's going to be basic HTML reading, and posting based on like a browser, (it looks for tags, such as <New Topic> but with automated functions crafted specifically for Blogger.
Basically, if you coded it in VB, you would specify the location to create a new post, such as blogger.com/newpost (w/e), and tell the name of the field where the it should get whatever you posted inside for the title in the application, and post it inside the field that corresponds with the title.
Basically a hidden automated process.