They are the class of errors that occur when a highly qualified and suitable candidate applies but is not selected, usually for unfair reasons. Their converse are Accept Errors which occur when an otherwise underqualified and/or unsuitable candidate is accepted.
In statistical terms, it is a Type I error, given a null hypothesis that the applicant is not outstanding (i.e. the hypothesis that is likeliest to be true).
Reject errors are problematic not just because of opportunity loss but because one company’s errors may prove to be to another’s advantage, thereby increasing vulnerability to competition. This is an especially serious problem given today’s situation of scarcity of skilled personnel.