Spectrum of Awareness
"Most people, at least in the globally northern world, tend to be living a life of speed and distraction... The worlds we inhabit are practically invented to keep us from looking inward." - Diana Winston
There are different ways of being aware in meditation.
As an analogy, imagine that you are looking out the window at a busy street.
If you can do so right now, you can try each type of awareness as I describe it.
The first type of awareness is called focused attention, in which you focus on a single car from the moment it enters your window frame until the moment it exists. Then you choose the next car and do the same.
The second type of awareness is called flexible awareness, in which you follow a single car, but more loosely. Now, if your attention instead gets caught by a street sign or a yelling pedestrian, you let it go there. You notice wherever your attention is naturally drawn, and then after observing that new object, bring it back to the cars.
In the third type of awareness, called open awareness, you take in the entire view of the window. Instead of focusing on individual cars, you just take in the whole scene. You still let your attention wander to various objects, like the sky or the road, but unlike flexible awareness, you don't go back to watching individual cars. There's no anchor of attention.
And finally, the fourth type of awareness is called natural awareness. As you look out the window, you become aware of the fact that you are aware of some scene in front of you. You become aware of the awareness behind your eyes. You don't have to look too hard, as natural awareness is effortless, resting in a state of meta-awareness and taking in both the scene outside the window and staying aware of the very fact that you are aware of that scene.
If this fourth type of awareness isn't making sense, then let me put it this way. If you are looking out the window and taking in the whole view, and I ask you, "Are you aware right now?", You might respond: "Yes, I'm aware of the scene outside my window."
But how did you know that you were aware in that moment?
Because when I asked you if you were aware, you became all at once aware that you were aware. You observed your own awareness. It's that simple, and it requires almost no effort.
While focused attention hones concentration skills and increased brain activity in the corresponding dorsolateral prefrontal cortex, open awareness leads to a broader attentional scope than focused attention. 
One study found that focused attention is characterized by beta and gamma brainwave activity, while open awareness increases theta brainwave activity.  This just means that your neurons are firing in different rhythms and patterns depending on how you're using your awareness.
In other words, the spectrum of awareness has corresponding brain signatures. Similar to how different types of exercise work different muscles in the body, similarly the different meditation techniques that we're practicing here are exercising your brain in unique ways.
So why bother moving along the spectrum of awareness in the first place?
The first is that you're getting to know your mind better. By experiencing different states of awareness, you're becoming familiar with the vast terrain of consciousness.
The second reason why training along the spectrum of awareness is important is that you're learning to activate these different mental states at will, harnessing the full power of your mind.
MENTAL FITNESS EXERCISE: Try out the window exercise (or your own version of it), sliding along the spectrum of awareness from watching individuals cars/objects, to flexibly letting your attention wander, to taking in the whole scene, and finally becoming aware of your awareness itself.
 Lippelt, et al. "Focused attention, open monitoring and loving kindness meditation: effects on attention, conflict monitoring, and creativity–A review." https://www.frontiersin.org/articles/10.3389/fpsyg.2014.01083/full
 Travis, et al. "Focused attention, open monitoring and automatic self-transcending: categories to organize meditations from Vedic, Buddhist and Chinese traditions." https://www.sciencedirect.com/science/article/pii/S1053810010000097