When we first started forming as a community there were many different projects working aspects of user-centric identity – and these different projects were using different words to talk about the same things and in some cases the same words with different meanings. Developing a shared language we used to talk about identity ideas/concepts was one of the first things that happened – so that we could get to coherently talking about the different proposals could converge.
This was not meant to be used to talk with "regular people" but rather this community of specialists to talk about detailed specifics of identity systems.
Agent: A computer system or device that has been delegated (authority, responsibility, a function, etc.) by and acts for a Party (in exercising the authority, carrying out the responsibility, performing the function, etc.).
Entity: A person, physical object, animal, or juridical entity
Party: A natural person or a juridical entity.
Relying Party: A Party that makes known through its Agent one or more alternative sets of Claims that it desires or requires, and receives through this same Agent a Digital Identity purportedly including the required Claims from a Digital Identity Provider or other Agent of another Party.