The Saving Throws entry is reserved for creatures that are adept at resisting certain kinds of effects. For example, a creature that isn’t easily charmed or frightened might gain a bonus on its Wisdom saving throws. Most creatures don’t have special saving throw bonuses, in which case this section is absent.
A saving throw bonus is the sum of a monster’s relevant ability modifier and its proficiency bonus, which is determined by the monster’s challenge rating (as shown in the Proficiency Bonus by Challenge Rating table).