UID
User and group ID's (UID and GID) are unique integers used to identify users and groups in a Linux system.
Each user has their own unique integer identifier (UID).
Each group also has their own unique integer identifier (GID).
File system objects, such as files and directories, can be owned by users or groups. Users can be members of groups and where this is the case, the group permissions on a file system object can be used to grant access to that object (e.g., to read it) to members of that group.
In CSE, users are typically authenticated via UNSW's own Active Directory (AD) service but as this is primarily a Window service it doesn't natively support the UID's and GID's required by Linux systems so these are provided, once a user has successfully authenticated to AD, by CSE's own UDB.