Equites were Roman horsemen or knights. The name is derived from the Latin for horse, equus. The equites came to be a social class. A single member of the equestrian class was called an eques.
Originally, there were supposed to have been 300 equites during the time of Romulus. 100 were taken from each of the three tribes Ramnes, Tities, and Luceres. Each of these patrician hundreds was a century (centuria) and each century was named for its tribe. They were called "celeres." Under Tullus Hostilius there were six centuries. By the time of Servius Tullius there were 18 centuries, the last twelve drawn from the richest, but not necessarily patrician, men.
The equites were originally an important division of the Roman army, but over time, they lost their military prominence moving to the wings of the phalanx. They still voted first in the comitia and kept two horses and a groom each -- more than any others in the army. When the Roman army started to receive pay, the equites received three times that of the ordinary troops. After Punic War II the equites lost their military position.
An eques was bound to a certain number of campaigns, but no more than ten. Upon completion they entered the first class.
Later Equites had the right to sit on juries and came to occupy an important third place in Roman policies and politics, standing between the senatorial class and the people.
Disgrace and Dismissal:
When an eques was deemed unworthy, he was told to sell his horse (vende equum). When no disgrace was involved, someone no longer fit would be told to lead his horse on. There was a waiting list to replace the dismissed eques.