This means they wrote in the languages spoken by the common people of their respective countries, rather than in Latin, which was the traditional language of scholarship and high culture.
Here are some examples:
* Italy: Dante Alighieri wrote *The Divine Comedy* in Italian.
* England: William Shakespeare wrote his plays in English.
* Spain: Miguel de Cervantes wrote *Don Quixote* in Spanish.
* France: François Rabelais wrote *Gargantua and Pantagruel* in French.
This shift from Latin to vernacular languages opened up literature to a much wider audience, contributing to the flourishing of Renaissance culture.