YMYL (Your Money or Your Life) refers to topics affecting money, health, safety, law or important life decisions. E-E-A-T matters especially for these topics.
Google uses the term for topics where inaccurate information could cause real harm, for example health, finance and pensions, insurance, law, safety, major purchasing decisions and politically or socially sensitive subjects.
Because the risk is high, visible , traceable sources, and clear responsibility are particularly important. A YMYL guide without a visible author and without cited sources is considered especially critical.
As a rule of thumb:
the more sensitive the topic, the more important authorship and evidence become,
the greater the business or personal impact, the stronger need to be.
Not every page is YMYL; simple product or service topics face lower requirements than medical, financial or legal content.