Presentity is an term used to describe an entity

Entity

An entity is something that has a distinct, separate existence, although it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.An entity could be viewed as a set...

 that provides presence information

Presence information

In computer and telecommunications networks, presence information is a status indicator that conveys ability and willingness of a potential communication partner—for example a user--to communicate...

 to help other entities, such as individuals, know whether it is acceptable to initiate a communications session, such as a phone call, a videoconference or an instant message session. The word is a combination of words "presence" and "entity" and was first introduced in RFC

Request for Comments

In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...

 2778.

Presentity usually refers to a human

Human

Humans are the only living species in the Homo genus...

. In this case presence information describes availability and willingness of this human to communicate

Communication

Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...

 via set of communication services. For example users of an instant messaging service

Instant messaging

Instant Messaging is a form of real-time direct text-based chatting communication in push mode between two or more people using personal computers or other devices, along with shared clients. The user's text is conveyed over a network, such as the Internet...

 (such as ICQ

ICQ

ICQ is an instant messaging computer program, which was first developed and popularized by the Israeli company Mirabilis, then bought by America Online, and since April 2010 owned by Mail.ru Group. The name ICQ is a homophone for the phrase "I seek you"...

 or MSN Messenger) are presentities and their presence information is their user status (online, offline, away, etc.).

A presentity can also refer to a group of humans, for example a collection of customer service agents in a call center

Call centre

A call centre or call center is a centralised office used for the purpose of receiving and transmitting a large volume of requests by telephone. A call centre is operated by a company to administer incoming product support or information inquiries from consumers. Outgoing calls for telemarketing,...

. This presentity may be considered available if there is at least one agent ready to accept a call.