If foreign input is made comprehensible, students will be able to turn it as real intake they can (subconsciously) process and work with. Overtime, this type of exposure provides the fundamental data required for building intuition (mental representation) of the language.
Once students begin to build the intuition of the language and feel “click” with the language, they can gradually tap for self-expression and naturally produce output. Another way to state this is that learner production of language is allowed to emerge on its own, as they are compelled to speak their mind.
Naturally, when we have received enough comprehensible input, and build the intuition of the target language, our brain will be able to run in reverse. Our target language will start spilling out of us.
Once we reach this point, we’re ready for output. We’ve spent all this time building a pool of latent ability through input. The next step is to convert that latent ability into output ability.
So exposing yourself to these situations that cause your brain to search through your pool of acquired language and make those words and phrases available to you for output is the way to develop output ability.
Sometimes, our brain won’t be able to find the right thing to say or write. These moments show you where you haven’t yet acquired the necessary language. Armed with this knowledge, you can target your immersion and fill in the gaps. This output/input loop allows you to quickly achieve basic fluency.
Therefore, we need to spend more time on student comprehension (through listening and reading) in order to build their intuition of the language, rather than immediately embark on the drilling of the language production (speaking and writing) itself.