Saints, like angels, traditionally come in “categories”. There are cherubim, seraphim, powers, thrones, dominations, angels and archangels, and, similarly, there are apostles, martyrs, confessors, doctors, bishops, monarchs (kings and queens), popes, Religious and virgins. (Incidentally, “confessors” here does not mean those who administer the Sacrament of Reconciliation but those whose lives bear a heroic witness that might have led to martyrdom but did not.) Each saint is placed in one of these categories.
This can lead to some oddities – Joan of Arc is in the category of “virgin”.