The Knights Templar were a chivalric military order of monastic knights who famously wore white tabards emblazoned with a red cross. Like all military (and indeed monastic) orders they had a strict hierarchy made up of three main "ranks".
The ranks of the Templars consisted of: the noble knights, the non-noble sergeants, and the chaplains.
Since the Templars did not perform knighting ceremonies, anyone wishing to become a knight within the Order had to already be a knight before joining.
These noble knights were the most visible branch of the order, and are the ones who wore the famous white mantles to symbolize their purity and chastity. They were equipped as heavy cavalry with each knight responsible for three or four horses and one or two squires.
Squires were generally not members of the order but were instead outsiders who were hired for a set period of time.
Beneath the noble knights were the sergeants. These were drawn from non-noble families and brought vital skills and trades from blacksmiths and builders to farmers and administrators. The sergeants were often the ones responsible for the daily running of the Order's many European properties.
In the Crusader States, the Sergeants fought alongside the noble knights as light cavalry. Surprisingly, several of the order's most senior positions were reserved for sergeants, including the post of Commander of the Vault of Acre, who was the de facto Admiral of the Templar fleet. The sergeants wore black or brown instead of white.
From 1139, chaplains constituted a third Templar class. The chaplains are probably the least known of all the Templar ranks and were, as the name suggests, ordained priests who cared for the Templars' spiritual needs. These "Templar priests" would not have joined their noble and non-noble brothers on the battlefield.
All three ranks of brothers wore the order's red cross.