One particularly extreme group of Zealots was also known in Latin as sicarii, "daggermen" (sing. sicarius), because of their policy of assassinating Jews opposed to their call for war against Rome. Some have speculated that the name of Jesus' disciple Judas Iscariot is a corruption of this term - "Judas the Zealot".
The Zealots were opposed to Roman rule and sought to eliminate it by violent means. At the time of Jesus Christ their activities were limited to raids on Jewish settlements and eliminating Jewish collaborators (tax collectors, like Matthew, were often collaborating with the Romans)
The Zealots had the leading role in the Jewish Revolt of CE 66. They succeeded in taking Jerusalem, and held it until 70, when the son of Roman emperor Vespasian, Titus Flavius, recaptured the city and destroyed the Second Temple.
The Jewish Revolt was quickly suppressed and the Zealots lost all their influence and finally vanished.