A blog is not a business by definition, but many bloggers view their blogs as businesses. This is because many bloggers use their blogs to make money through the sale of advertising space, sponsorships, and other forms of monetization. However, there is no set rule defining whether or not a blog is considered a business.
In general, if a blogger is primarily generating income from the sale of goods and services, then their blog may be considered a business. Additionally, if a blogger possesses significant assets (such as a website or an online store) related to their blog, then they may be considered to be running a business.