The Plebeian Tribune is also known as the tribune of the people or the tribune of the plebs. The plebeian tribune had no military function, but was strictly a powerful political office. The tribune had the power to help the people, a function called ius auxilii. The body of the plebeian was sacrosanct. The Latin term for this power is sacrosancta potestas. He also had the power of the veto.
The number of plebeian tribunes varied. It is believed there were originally only 2, for a short time, after which there were 5. By 457 B.C., there were 10. [Smith Dictionary.]
The office of plebeian tribune was created in 494 B.C., after the First Secession of the Plebeians. In addition to the two new plebeian tribunes, the plebeians were allowed two plebeian aediles. The election of Plebeian Tribune, from 471, after the passage of the lex Publilia Voleronis, was by a council of plebeians presided over by a plebeian tribune.
When the plebeians seceded in 494, the patricians granted them the right of having tribunes with greater power than the patrician tribal heads. These tribunes of the plebs (plebeian tribunes) were powerful figures in Rome's Republican government, with the right of veto and more.
A patrician, Claudius Pulcher had himself adopted by a plebeian branch of his family so he could run for the office of plebeian tribune under the plebeian name of Clodius.