The obligation for the megillah reading is for one to read the scroll. If one cannot read it, one listens to the blessing and then listens to the reader read it.

But what is the nature of "listening"? If I am in a room and the reader reads and I am awake, is my hearing all the words without any particular attention being paid the same as listening? If I have intent to be yotzei during the bracha then do I have to be focusing for each word or is it enough to have the words simply said in my presence with no interruption?

My underlying obligation is to read the words myself, but in the same way, is there a difference between reading and focusing on each word and simply reciting (because one has read it so many times that it is almost automatic)?

I fear that if I zone out a bit when listening, or "coast" when reciting, I might invalidate an entire complete obligation so I am wondering what kind of awareness one has to have during the process.