ArcGIS Mission Responder is the mobile app that allows users in the field to participate in active missions. It relies on ArcGIS Mission Manager or ArcGIS Mission Server to create and activate missions, but Responder is its own separate application, with unique capabilities and uses.
Responder is designed for mission participation, not creation. The app cannot build or edit a mission, and it only has access to missions that have been placed in active status.
If this is your first time using Responder, it is recommended that you read Access ArcGIS Mission Responder, followed by Participate in a mission with ArcGIS Mission Responder to gain a better understanding of how to use the app.