Consciousness-raising, also known as awareness-raising, is part of the process a learner can go through with new language. They first become aware or conscious of the new language, then recognise and distinguish it, then produce it.
Learners studying the contracted form 'didn't' first may become aware that the form exists in English, then recognise it when they hear it and distinguish it from other sounds, and then produce it themselves.
In the classroom
Often a teacher decides to encourage learners to notice new language, or to recognise it, rather than produce it themselves. Two examples could be recognising phrasal verbs, and guessing their meaning context, or distinguishing the words said in connected speech.