The private railways of Germany have been ordered by type of activity:
builder contains companies that build rolling stock
freight contains freight operators that have their own lines
historic contains companies that do no longer exist
industry contains industrial networks
lease-hire contains companies that hire/lease stock to others (mainly for operating track maintenance trains)
narrow_gauge contains all companies that operate narrow gauge trains (both passenger and freight)
open_access contains operators that use DB Netz infrastructure to run (long distance) freight trains
passenger contains companies that (mainly) operate passenger trains
port contains operators that run port/harbour lines
work contains track maintenance and building companies

---