From AnthroWiki

Entity (Latinentitas, from ens "being") is a philosophical-ontological term denoting an individual "being as distinct from the general essence of a thing" or also those essential determinations that constitute its unique identity. What is decisive here is that it is, i.e. exists in some form, whether as a physical or non-physical entity, but not what it is, in the sense of its subordination to a general concept. An entity is unique and uniquely identifiable. It can be a thing, a clearly identifiable object, a clearly identifiable state of affairs or a clearly delimitable concept, a closed unit or whole, i.e. material or immaterial, concrete or abstract objects, properties, processes, etc. The expression thus denotes the real or imagined or conceived being of something in its unique thisness (Latinhaecceitas), to which one can only point by way of indication, in contrast to the whatness (Latinquidditas) or essence (Greekοὐσία ousia, Latinessentia), the universal suchness that it has in common with other entities of the same species or genus.

In computer science, this means an individual information object about which data are collected or processed and which can be uniquely identified via a Uniform Resource Identifier (URI).