This term refers to a list of successful candidates/laureates who have passed the selection process for a particular competition, but have not been immediately appointed to a position. These candidates are placed on the reserve list, which serves as a pool of potential candidates for future job openings in the European institutions and contains information on the profile, competencies, and availability of all the successful candidates in a particular selection procedure. 
Being on a reserve list is not a guarantee of recruitment, but on average 50% of candidates are recruited within 7 months.