As your cat's parent/guardian and companion, you know their habits both in and out. You know their favourite place to sleep, their favourite foods, what they like and dislike. You know how they like to be entertained and you also know when they are feeling not quite right.
This bond you have created goes both ways. Your cat knows many things about you as well. When you are feeling under the weather, you cat is there to comfort you. When you are in a bad mood, your cat is there to cheer you up, even when at first it seems like they are annoying you, there persistence always seems to get the better of your bad mood and cheer you up.
Does you cat know when you are due to come home from work, and is waiting at the door for you? Does your cat know when something is up, (like taking your cat to the vet, or to the holiday resort) and they hide or don't come home when they normally do.
I am willing to bet that your cat knows you pretty well!