A Deshna is a type of religious speech in Prakrit. According to Jainism, after a Tirthankara gains infinite knowledge, in his honor, the heavenly beings create a place called samavasarana, where all creatures are welcomed (including non-human creatures, humans, and angels) for Tirthankara's speech. This speech is understood by everyone in their own languages. These types of speeches are known as deshnas.
References
Deshna Wikipedia(Text) CC BY-SA