A structured explanation of what a Claimant or a Comparator does, to what, with whom, when and with what outcome. That is, a description of the tasks and activities that they carry out on a specified date or over an agreed period of time.
It is a separate document from the Job Analysis and the Person Specification. Although, in practice it is often the case that two or three of these documents are combined as a single document, in the context of an equal value case, it is important to bear in mind the fact that they are concerned with three different issues.
In an equal value case the Job Description is the primary factual information on what is done, where, by whom, how and with what outcome. Responsibility for its collection is the parties.
The Person Specification is focused on the characteristics of an individual (length of hair, appearance, colour of skin). As such, it is open to a wide range of personal prejudices and idiosyncrasies. Consequently, it is normally ignored in equal pay cases.