In general, the terms commisioned officers and warrant officers come from the english structure.
Staff rank - officers of one star and above (full colonel and up) these keep their rank upon retirement.
Commisioned officers - these have been commissioned by the Head of State to carry out certain duties. They can resign that commission, but it is up to the head of state to accept it.
Warrant Officer - these have a warrant to carry out duties. The difference is that to be commisioned has a historically higher importance.
(Non- Commissioned) Officers - These are common soldiers recognised for their experience, training and ability who are promoted to help organise soldiers and maintain discipline.
Soldiers - they are enlisted and are contracted to perform duties as required.
NCO's and soldiers are discharged when their term of enlistment is complete.
Comissioned officers wear rank on the shoulder, others wear their rank on their arm. The first enlisted rank was a chosen man who wore a ribbon tied around his arm. This was called tape, and later called stripes.
The first commissioned rank was a Lieutenant to the King and they would typically be in charge of an entire wing of the army. To sort out hierarchy amongst Lieutenants, some would be given a Captaincy. The term General was more an institutional appointment, as in post-master general or attorny general, but as armies required more logistics due to their size, generals made their appearance in the army.
Colonel - can talk to God over the phone and is on first name terms with God's secretary
Major - sees God at the annual Christmas party, but tries to keep the conversation to a minimum
Captain - tries to avoid running into God around the base in case God asks a pertinent question
Lieutenant - trembles in fear and stutters if God is mentioned
Second Lieutenant - wets himself and runs off screaming if God is mentioned
Regimental Sergeant Major - he is God