PICO (Population, Intervention, Comparison, and Outcome) is primarily used among biomedical researchers, although other areas of science use PICO to study non-human health. PICO and its variations (PICOT, PICOS, PIOS, etc) are used for asking focused clinical questions for both quantitative and qualitative reviews. Rayyan's PICO implementation today is focused on biomedical use cases, but may provide some value for other researchers.
A more thorough explanation of PICO can be found here (published by The Cleveland Clinic).
The graphic below explains common uses of each letter of PICO in the biomedical context. Source here.