Phonemic awareness is the ability to hear and manipulate the sounds (phonemes) of our language. It is an essential skill in learning to read and spell. Teaching phonological and phonemic awareness is done in the absence of written text, in other words, it is done auditorilly. When we combine teaching the sounds and the letters—that is called phonics.
The video above does a very nice job at explaining phonemic awareness and providing ideas for ways to promote your child's learning of this skill. In the "Professionals" portal of this website, you will find much more about Phonemic Awareness.