Reference Data
User-extensible lookups underpinning treaties, programs, and risk lines. Two fixed enums (customer_type, primary_excess) live in the schema only.
Business entities
Organizations (insurers + MGAs) and the underwriting programs you write under them.
P&C taxonomy
Risk Category → Statutory Line → Coverage → Peril (per docs/Taxonomy/).
Other reference data
Geography, currency, and miscellaneous lookups.