Armor (x) reduces the damage taken to this monster by x. So because Receptionist 2 has Armor (1), all damage it takes will be reduced by 1. That makes this monster very useful, despite it just having 4 HP, as it can only be one-shot from 5 DMG or more. Not to mention, cards like Undyne's Spears have no effect on it, similar to Mad Dummy.
It also has Taunt, so it must be targeted by monsters. With its stats and Armor, it's also able to barely survive an attack from Tsunderplane. (Tsunderplane won't die either, but that wouldn't matter anyway as its Dust can't harm this.) But because it has 2 ATK, it's weak to Muffet's Pet.