Population Health refers to study of health events, patterns and conditions across a population of certain type. This is still a new area of practice in the industry especially when it comes to Genomics.
However, the study of population data with respect to which and how many bio markers are observed for a given condition, offers useful base lines since every genome tends to exhibit unproven susceptibility to several conditions at varying degrees.
By base lining to a given population, we can have some idea of relative risk of a given condition within the population; more importantly, an individual genome can be evaluated against a population benchmark to have an idea of which conditions and to what extent it is at risk for a health condition.
For example, if cancer is the most prevalent in a population type and an individual has the quantity of bio markers that is far below the population benchmark for cancer, that individual may prioritize another condition that seems to indicate more of a risk relatively.
This not only allows for trying to understand where to focus but also to search for available clinical trials which are often free and local to an individual.
Quibble bases its population health cutoffs based on lab type which means 23&me genomes are assessed against the genomes uploaded at 23&me genomes; same applies for ancestry.com.
Please note that both have different levels of sensitivities for health conditions.
caution: population types are never completely relevant or indicative of possible risk for a condition for a given individual; as such, looking for a clinical trial or qualifying for one should be pursued only with your physician's guidance.