Orta can be roughly translated as regiment but an orta do not have a fix number of soldiers. It can be 50 soldiers or several thousands. Oda means room. Which simply means the soldiers who live in the same room/tent. Every room/tent has its commander and commander lives and eats with the soldiers.

Other than several Guard  Ortas permanently stationed at the capital no Orta was stationed permanently at some location. Most of the garnisons had soldiers from different Ortas.

 

Camelmen Ortas were the ones which originally founded to guard the baggage train. In time their duty changed.

Solak Ortas are the Guard units. The word of "Solak" means left-handed. And exactly half of the soldiers of these Ortas were left-handed. When the Sultan passed someplace, left handed soldiers stayed on his left, right handed ones stayed on his right. And they secured Sultan himself. No Sultan after Murat I (who lived before Solak units were founded)  in Ottoman history assasinated by someone other than his solaks.

 

All Janisaries were followers of Bektasi sect. So they had their own religios officials. 99th Orta was the Orta which guarded their own highest ranked religious-officer.

 

Many Ortas were founded for a specific duty. In time when their duty become obsolote they served in a different capacity.

They had archer Ortas, musket Ortas and armoured Orta. During 17th century all Janissaries started to use muskets. There were naval Janissaries which were used as marines. There were dog keeping and hawk keeping ortas which were part of sultan's hunting group. (Ottoman sultan's loved hunting).

 

Every command position is also referred to a specific duty. For example the Orta commander Corbaci literally meant "the soup-giver". During meal time he personally brought the food to the Orta.