Professor Mark Williams, former director of the Oxford Mindfulness Centre, says that mindfulness means knowing directly what is going on inside and outside ourselves, moment by moment.
"It's easy to stop noticing the world around us. It's also easy to lose touch with the way our bodies are feeling and to end up living 'in our heads' – caught up in our thoughts without stopping to notice how those thoughts are driving our emotions and behaviour," he says.
"An important part of mindfulness is reconnecting with our bodies and the sensations they experience. This means waking up to the sights, sounds, smells and tastes of the present moment. That might be something as simple as the feel of a banister as we walk upstairs.
"Another important part of mindfulness is an awareness of our thoughts and feelings as they happen moment to moment.
"It's about allowing ourselves to see the present moment clearly. When we do that, it can positively change the way we see ourselves and our lives."
How mindfulness helps mental wellbeing
Becoming more aware of the present moment can help us enjoy the world around us more and understand ourselves better.
When we become more aware of the present moment, we begin to experience afresh things that we have been taking for granted.
"Mindfulness also allows us to become more aware of the stream of thoughts and feelings that we experience," says Professor Williams, "and to see how we can become entangled in that stream in ways that are not helpful.
"This lets us stand back from our thoughts and start to see their patterns. Gradually, we can train ourselves to notice when our thoughts are taking over and realise that thoughts are simply 'mental events' that do not have to control us.
"Most of us have issues that we find hard to let go and mindfulness can help us deal with them more productively. We can ask: 'Is trying to solve this by brooding about it helpful, or am I just getting caught up in my thoughts?'
Mindfulness is recommended by the National Institute for Health and Care Excellence (NICE) as a way to prevent depression in people who have had three or more bouts of depression in the past.
See the NICE guideline on depression in adults.