When one says that a blog is interactive, they are essentially saying that the content on the blog is meant to be interacted with. This could mean anything from leaving comments on posts to sending feedback to the author of the blog.
Basically, if there are ways for readers to engage with the content on the blog, then it can be said that the blog is interactive.
While this might not always be the case, it is generally accepted that a blog that is interactive is more engaging and user-friendly. This means that readers will likely stay longer and visit more often than those who read blogs without any kind of interaction.
Additionally, it can lead to a stronger connection between the author of the blog and their readers, which can only be beneficial for both parties.