From Halopedia, the Halo wiki
A data module is a small personal computer with numerous functions utilized by the Kig-Yar, similar in application to a human data pad. Data modules can be used to store information and files, including job listings and contracts available for Kig-Yar. They also store location data, containing coordinates and descriptions of various locations in known space. Banking could be done on a data module; one individual sends currency to another module and as soon as the signal from the first module reached the second, the second individual's bank balance would be updated.
List of appearances