YMYL acronym stands for "Your Money Your Life" and as far as I know this filter has appeared in far 2013 year, but has undergone a few major updates since.
Actually google guidelines does exist but for so-called "quality raters" not for webmasters. The YMYL term we can find in one of 2013 year's versions of “Search Quality Ratings Guidelines”, that was leaked online. It says, quoute:
There are some pages for which PQ is particularly important. We call these pages Your Money or Your Life (YMYL) pages. They are pages that can have an impact on your current or future well being (physical, financial, safety, etc.).
So, we can assume, that YMYL pages should come from reputable websites and the content should be created with a high level of expertise and authority.
Before thinking about how to pass this YMYL filter you need to ensure that your site falls in one of these categories (according to that document):
Pages that solicit personal information, such as personal identification numbers, bank account numbers, drivers license numbers, etc., which could be used for identify theft.
Pages used for monetary transactions, on which users might give their credit account or bank account information; for example any page that allows you to buy something.
Pages that offer medical or health information that could impact your physical well being.
Pages offering advice on major life decisions, such as pages on parenting, purchasing a home, a vehicle, etc.
Pages offering advice on major life issues that could impact your future happiness and finances, such as pages giving legal or financial advice.
The final thoughts we can think is that:
Initially those guidelines is made for Google's search quality raters. And it doesn't mean that this may have direct impact on rank.
Still, it's obvious, that eventually it will matter to have trusted and authorited content on your site. Especially if it may have financial or health consequences for it's readers.