Awareness is you. The original you that contains all the rest of you or the whole of you. In other words Awareness is the aspect of you that makes you alive. When Awareness returns back to your body and to the here and now it is presence. When the awareness remains present in the activity you are engaged in, it is mindfulness. In other words when you bring presence into your activity or work that would be mindfulness. It is a bit difficult to grasp because we are using our logical, analytical mind which is one small aspect of awareness to understand and create a concept out of it. It is difficult but not impossible to do so and it becomes easier when you first realise all these three experientially.
I will elaborate all these with examples and contrasts. Before I do that, let us do an experiment to bring your awareness back into presence and mindfulness with this practice. Please read the following linked article and practice FGCB for a minute and then listen to the linked audio below that to practice witnessing four simultaneous activities for five minutes and then get back to the remaining part of this answer for detailed explanation.

Selvan Srinivasan · 1y
What are some breathing exercises for beginners who struggle with focusing on their breath while meditating?
Do this for just three minutes and see if it helps. Sit on a straight back chair with feet flat on the floor, the entire soles of the feet from tips of the toes to the heels firmly contacting the floor. Keep your back erect, you may place a cushion behind your back for support if required but do not lean back on an inclined backrest of the chair. Let your head be held straight, neck straight, shoulders square and relaxed. You may tilt the head very slightly downward to gaze at a point on the floor in front of you a few feet away from you. Keep your eyes fixed on that spot for the three minutes without moving your eyeballs. Allow your eyes to be half open and half closed and hold that spot in a gentle gaze and not a stare. You are not looking there to see something but simply holding that spot in a gentle gaze. Exhale with a loud sigh from your mouth and use gentle effort to empty your lungs as far as possible without straining too much. Then relax your body and allow the inhale to happen effortlessly and soundlessly through your nostrils. When you sense that the inhale is over, do not put any further effort to breathe in but repeat the exhale from the mouth with the sound and gentle effort. I call this conscious breathing. Effort only for the out breaths and allowing in breaths to happen effortlessly. This entire process is called FGCB or fixed gazing with conscious breathing. You may set hourly reminder alerts on your smartphone and repeat this 3 minute FGCB every hour throughout the day today and see how it helps with calming your mind. This is a powerful grounding practice and you can do this even when you are driving and waiting for the red signal to turn green. Allow any such interruptions in your day to remind you to come back to the practice of FGCB repeatedly. For more information and plenty of free resources to aid with the practice of meditation and deep healing, please visit my website.
Selvans Short Meditation – Witnessing The 4 Simultaneous Activities
This is a five minutes short guided meditation for slowing down the racing thoughts in your mind and coming back into grounded presence within yourself with a quiet mind. You can do this at any time d
Now let us see if we can explain awareness in the context of spiritual wholeness. Awareness is a being state, it is not a doing state involving the thinking-mind. Activities such as paying attention, studying, looking, noticing, taking note, concentrating, thinking, understanding, etc are all doing activities. You engage your mind to do something. When your mind shifts from the doing mode to the being mode you are Awareness. The life in you is the awareness in you. You don’t have to do anything to simply be aware of all that is arising and happening in the present moment. You only have to do something when you need to compare what is happening with your experience and your needs and see if it is ok or not ok. Awareness is the witness state of you, the basic being state of you.
Presence is when you bring the Awareness to the here and now. This implies that we are not present most of the time. Where did we get lost if we do not have presence right now? In our thoughts, in the past or the future. Past and future are simply constructs of the thinking mind and they do not exist in reality except as thoughts in the mind. When you bring presence back to your body which is always in the here and now, you connect to the frequency of the vibration of earth energy. This is called grounding. Please read the first two articles in the posts section of my Quora profile titled Presence and Grounding to get more clarity around this.
If you can bring the presence into whatever you do, that would be mindfulness. I used to be an absent minded professor all the time few years ago and I would drive and reach my destination without having any memory of the drive because I would be lost in thoughts all the time. Sometimes I would reach somewhere others than where I wanted to go! I would also get involved in frequent minor road accidents or skipping the traffic signals and getting fined by the traffic police. It became too much and then I completely stopped driving and hired a driver. But now in the past five years I have not met with any road accidents or had a single traffic challan because I am able to bring mindfulness into my driving with ease.
The article linked below suggests a practice that could help you with this. A better option would be to enrol into my course called Awareness Journey.

Selvan Srinivasan · 1y
How can I meditate 24*7?
Yes it is possible to hold a background state of Awareness or be present in the here and now or be connected with your grounding or meditate 24×7 as you call it and yet be completely focussed on something else in the