Simon appears in every list of the twelve, always with an epithet to distinguish him from Simon Peter, and always at or near the end of the list. Matthew and Mark call him the Cananaean (Kananaios); Luke and Acts call him the Zealot (Zelotes). The two are the same word: Kananaios is a Greek transcription of an Aramaic term for zealous or enthusiast, which Luke has simply translated. It has nothing to do with Canaan or with the town of Cana.
What the word signified for Simon is genuinely uncertain. Later readers have often taken Zealot as a party label and cast him as a former member of the armed nationalist movement that resisted Rome, an appealing picture, since it would set a revolutionary beside a tax collector among the twelve. But that organized movement, the Zealots proper, is usually dated by historians to the revolt of the 60s, a generation after Jesus, which makes the party membership anachronistic. More cautious scholars read the epithet as describing Simon's temperament or his zeal for the Jewish law rather than a political affiliation.
Apart from the lists, the New Testament records nothing whatever of him, no word, no act. He is a name, an ambiguous nickname, and a gap that tradition rushed to fill in incompatible ways.