Data Dumps are weekly updates and Messages that are sent to Ares Mission crewmates as they conduct there mission. When the crew is 3,844,000 km from Earth, the crew uses video and audio chats, mush like updates on the ISS to communicate with Mission Control. However, once the crew exits this window, the communication delay is too great, and the crew switched to text messages to relay information and telemetry to mission control.
Data dumps are an extension of this, where large files are dropped off all at once, and are downloaded onto Hermes computers, or Hab files. Data Dumps include mission schedules, and scientific objectives. As well as personal videos and messages sent from family and friends.