This document defines participatory archives as organizations, sites, or collections where people other than archives professionals contribute knowledge or resources to increase understanding of archival materials, usually in an online environment. It discusses why clear definitions are needed for participatory archives and participation, distinguishing the latter from simple engagement. Participatory archives harness people's cognitive surplus to distribute curation and allow remote, occasional contributions to broaden archival understanding. They can be place-independent, combining in-person and online participation.