It is essentially the state of being in the latter portion of one's life and being looked to for leadership of either a passive or active nature by your peers and\or subordinates due almost exclusively to this fact.
Once having met the peculiar requirements of their individual groups, however, all elders are generally expected to mentor, share their experience, create a sense of oneness for their followings and, most especially, act as the spiritual embodiments of their communities.
An example of informal elderhood is the role of the matriarchal grandmother as it appears in many parts of the global South.
In the absence of viable male alternatives or even in the presence of them, grandmothers in these areas tend to serve as both the de facto heads of their groups of descendants and the catalysts of their periodic reunions and meetings.
In such online communities elders are typically thought of as established members who are outbound, often due to unwanted changes they can't prevent.