A pilot is a preliminary investigation of the feasibility of a study, usually done on a small scale (10 or fewer subjects) which is exploratory in nature.  It is designed to help the investigator refine data collection procedures and instruments or prepare a better, more precise research design.  Such a pilot would not contribute to generalizable knowledge and therefore is not considered research and does not require IRB review.  Data collected from a pilot study cannot be used as research data.  

Medical interventions or interactions for research purposes, especially those involving invasive procedures, or piloting of procedures with vulnerable groups (e.g. children) do require IRB review regardless of the size of the study.