While an ontology is like a template, an instance is a specific occurrence of an ontology.
During configuration, the ontology 'Person' has been defined.
Whenever a person becomes part of a case, this individual will then be an instance of the ontology 'Person'. He or she will have a first and last name and other information that make that someone an individual instance of 'Person'. "Jonathan Griffin" could be one instance of the ontology 'Person', "Maria Lopez" another one.
As the case moves through the process, Atfinity will include all the information fields, roles, documents and proofs you have defined during the configuration for the ontology 'Person'. At the end of the case, all information about all involved instances will be known.