Mindfulness meditation is the practice of intentionally focusing on the present moment, accepting and non-judgmentally paying attention to the sensations, thoughts, and emotions that arise.
The aim of the body scan is to be aware of the different regions of your body, and allow yourself to experience how each part feels, without trying to change anything. Just being with what is there.
The body scan alternates between a wide and narrow focus of attention; from focusing on your little toe all the way through the entire body. The body scan trains your mind to be able to move from detailed attention to a wider and more spacious awareness from one moment to the next.
Above is a body scan meditation from John Kabat-Zinn, one of the main influencers for Mindfulness in the West. After doing the meditation, notice how different your body and mind feel. You are welcome to share in the comments below how it all felt.