Because real human beings leave data tracks through time as if they were disparate shadow personas, this entity allows the genealogical researcher to tie together data from different personas that he or she believes belong to the same real person.
GENTECH Genealogical Data Model 1.1 - from the Persona entity definition.
Personas are central to the evidence side of the database, they are used collect together snippets of information that refer to the same person. The evidence we have for our family histories is normally recorded in documents of some kind. As we interpret these documents we pick out the dates, places, names and relationships being used and the events being described, either directly or indirectly. We can associate these elements with personas that represent the people being described. The persona can then be linked to individuals, either when we are examining the document or at some time later.