Process Engine is one of Curator's back-end services, and is responsible for orchestrating Curator's workflows, managing several functions including ingesting content, exporting edited projects, archiving hi-res files, and much more.
End users will not have access to Process Engine and it is managed by a Curator System Administrator (e.g. the IT Team in your organization, or the Tech Support team at IPV or your integration Partner if a managed service is being provided).