Mindfulness is a meditation technique, where you cultivate your mind to be in the present time (NOW) and in full awareness of your inner experiences example as bodily sensations, feelings, thoughts and memories.
You simply observe without any judgements or change. Meaning if something itches, try to just be with this sensation, don’t scratch or follow the notion.
Cultivating means to practice, like brushing your teeth or learn to paint - it is a process that does not come from one day to the next.
We need to be aware of our daily situation, weather we work or not - we have permanently stimulation that arrives in our brain. Sitting down and doing meditation is the opposite and can be compared to a car driving at 200km/h stopping at once to zero. All the luggage and papers will fall to the front and maybe the car will also make a summersault.
The same happens with our mind. We sit down and suddenly all thoughts come, what we have to do, whom to call, to cook etc. all our nerves that were in movement suddenly feel twitches or itchiness - as a sign of SUDDEN relaxation - trying to keep us active and not calm.
In spite of all there sensations, we still try to stay with our breath in the now, not trying to change - but just to be with it