Mindfulness is awareness and complete consciousness of the present moment. Be it the place you are at, the work that you are doing, or the person you are talking to, mindfulness is all about giving in to the present moment.
Mindfulness is also about balance, which means not getting overwhelmed or overreacting to a situation or to what is happening around.
Being mindful is to be aware of what you are personally experiencing with your entire being, i.e., your mind, thoughts, emotions, movements, and senses. Completely and wholly.
Mindfulness is an innate ability in each of us. Keeping the ability intact and bringing it up at your will is necessary, and only training and practicing mindfulness can do that for you.