The term "The Old Ones" refers to Beings old enough to know even the darkest secrets of the Universe. They are old enough to have acquired Immortality (if they aren't immortal in the first place) and take rarely interest in the games of the mortals, like regional politics. Old Ones are known to stay in the background, much like Gods. Their actions are more of influential origin and they only appear in front of people when it is personal business.
An Old One is strong enough and old enough to have acquired skills beyond the comprehensible. They are known to show strength and wits even better than their brethren usually portray. A few more modern thinking Beings call this Limit Break, a special power to break the bonds of limitations.
Even a more darker secret, some of the Old Ones broke even more bonds of being a sentient existence. Old Demons and Angels show the abilities of their other kin, even being able to use the powers of less powerful Beings, such as the shapeshifting abilities of a Harlequin.