Regional Internet Registries (RIRs), such as ARIN, RIPE, APNIC control the allocation of globally-routable address space. Internal IP address space (eg. RFC 1918) is also treated as an RIR within NetBox, and users can can create whatever RIRs they like.
Aggregates are assigned to RIRs, and typically, an aggregate will correspond to either an allocation of public (globally routable) IP space granted by a regional authority, or a private (internally-routable) designation.
Our fictional organization will be using RFC 1918 Private Address space for IPv4, which has the following Aggregates assigned to it: