Depending on the Nation, you can get a different Command rating for your ship between 1 and 4. This is randomly determined by ship, a bit like BFG. The rating is the number of dice you roll looking for a success.
A Command test represents a lot of intangible factors such as Crew skill, Officer skill, Morale, and even communications within a ship's design. Crew and Officers can get basic stuff done pretty easily as it is routine. Things like change speed, change altitude, turn, fire the guns, etc.
However, a Command is trying to go above an beyond the routine or do something under time constraints/stress. Things like crash dive, evasive maneuvers to avoid collisions, fire for effect, dedicated damage control, Reloading air torpedoes etc. A failure means that the crew and officers somehow got their wires crossed and were not able to execute the Command. This could be from poor execution, garbled orders, unclear orders, or the Command just never got there for some reason.
It is somewhat of a game abstraction to add elements of Command and Control and their failures. When you read a lot of Naval History, you find little mistakes like not sealing the magazine stores correctly, failure to repair some key damage, or not having a clear spotter, can be battle changers. This was a way to try and capture some of that "uncertainty" and "friction" that occurs in Naval warfare.