aids of a general officer or a flag officer

Officer

A Staff Sergeant is a noncommissioned officer, whereas a Captain is a commissioned officer.

Public Information Officer, Liaison Officer, Safety Officer

A Line Officer is in charge of troops and other ranks in the navy,

A Staff Officer is in charge of an auxilary or support section of a command.

The main difference is the line officer is in a more manager/leader position, The Staff Officer is like the lead supply guy or something similar.