The answer is: Only seven of one hundred and twenty plays survive today, and they are considered literary classics.
Sophocles is one of the three great ancient Greek tragedians, the other two being Aeschylus and Euripides, who wrote and lived during the 5th century BCE. Though so many of his works were lost, the seven that survived to this day are not only considered classics, but also foundational in regards to literature, the arts in general, and culture.
The seven plays that survive are: Oedipus Rex, Oedipus at Colonus, Antigone, Ajax, Women of Trachis, Electra, and Philoctetes.