Ask HN: Whats the diff b/w a lifestyle business, a side project, and a startup?

I asked this a few days back but got no replies. Then I asked it again with no replies. Three times lucky? :)

How would you define whether what you are building is a lifestyle business, side project or a startup? Are there any specific metrics which can be used to decide between the three? Are there any other categories that I have not listed?