Under the on-topic help page, insurance is not listed as something on-topic. However, I've noticed a many questions on insurance (it's also a tag).
Are questions about insurance on-topic, and if so, which category do they fall under based on the on-topic help page?
There are many types of insurance, but nearly all of them are related to finances. (Insurance provides a monetary benefit in the event of some loss.) Of all of the types of insurance, many of them are related to personal finance.
The basic on-topic litmus test for this site is this: Is it related to personal finance? Many insurance questions will be.
For example, questions about health insurance, life insurance, auto insurance, homeowner's insurance, renter's insurance, personal liability insurance and even extended warranties are all on topic here.
Questions about corporate liability insurance and worker's compensation insurance are probably off-topic, as they are generally business-related. However, sole proprietership/self-employed business questions are on-topic, so even these types of insurance might be the subject of an on-topic question.
