Identity Assurance is The ability for a party to determine, with some level of certainty, that an electronic credential representing an entity (human or a machine) with which it interacts to effect a transaction, can be trusted to actually belong to the entity. Proving you are who you say you are to a certain level of confidence.
Ref.: http://oixuk.org/wp-content/uploads/2016/02/Digital-Identity-Across-Borders-FINALFeb2016-2.pdf