To me, it appears that the most natural starting point for a discussion of longevity would be a discussion of centenarians. So for our purposes, we'll kick off this site with that.
Chances are, you should probably already know what a centenarian is, but for now, we'll discuss it for the sake of convenience. A centenarian is a person who has attained the age of 100 years, or to put it in another way, who has passed their 100th birthday. Since average life expectancies around the world are still well below 100, it should come as no surprise that the term is associated with longevity.
A supercentenarian is one who has lived to the age of 110 or more, which as we'll see later is MUCH rarer. Furthermore, just 2% of supercentenarians live to age 115.