#1 The Purpose of Your Blog
Blogs can be just about any topic but usually people who search about topics online want to solve a problem.
So the most successful blogs are those whose content is based on a particular goal. People who want to achieve that particular goal read those blogs.
This is important for having a connection between your posts and the brand name of your website. All posts being around a central goal, will make visitors click from one of your posts to the other.
For example, for some blogs their central topic is making money online, or making passive income, each of those posts is about a method to make money online so the visitors are likely to be interested in all of them.
This has to do with choosing a niche which is related about a goal that you want to pursue. This also has to do with audience research. You need to choose your target audience which is a group of people who aim to achieve the same goal.