Jesus acknowledges that he has spoken to the disciples in 'proverbs' and promises a time when he will speak plainly about the Father.
The statement helps explain why the disciples repeatedly struggle to understand images and sayings in the Farewell Discourse.
The Greek paroimia can mean a proverb, figure, comparison, or cryptic saying. John uses the same word for the shepherd imagery in chapter 10. It therefore need not mean a compact maxim like the sayings collected in the biblical book of Proverbs. The contrasting word for speaking 'plainly' conveys openness or clarity rather than figurative indirection.
Recognizing the term's range prevents readers from searching for a conventional proverb where John is describing figurative teaching more generally.
Jesus also presents understanding as progressive: the disciples have heard true teaching, but the significance of his death, resurrection, and return to the Father will make much of it clearer.