Language production is a concept in psycholinguistics that describes the stages of speech from the initial mental concept to the spoken or written linguistic result. Simply put, it is the process of communicating through language.
An example of language production at its base is simple. Picture a person thinking of an apple, then using their mouth to physically sound out the word 'apple', then another person hearing this and perceiving the sounds that make up the concept of 'apple', then they have the mental representation of the apple. This is the process of language production.