There are many sources of information about mindfulness, both in its originally religious form (Buddhism, Sikhism, Advaita Vedanta and others) and in its western secular form. Here are some brief videos on mindfulness as it is now often practiced in the west. The first one is an ultra-brief (60 seconds) description of mindfulness from Rush University in Chicago:
https://www.youtube.com/watch?v=qEw_TsEHqU8
Jon Kabat-Zinn, M.D., PhD. is the first man to extract mindfulness wisdom from Buddhist sources and apply it in the medical sphere. His Mindfulness-Based Stress Reduction training was that first application and has helped numerous patients with chronic pain (and other disorders) to manage their lives well. This brief (5+ minutes) video is a slightly longer outline of the practice of mindfulness:
https://www.youtube.com/watch?v=HmEo6RI4Wvs
One does need to be careful when learning mindfulness because there are now a large number of mindfulness sources and, sad to say, some of them are in it just for the money. A friend of mine who teaches Buddhism at a state college here in Florida calls that "McMindfulness." Virtually any wisdom from Jon Kabat-Zinn, Rick Hanson, Thich Nhat Hanh (and other teachers in the Interbeing tradition), Tara Brach, Pema Chodron and most anyone from the Insight Meditation Center are very knowledgeable and trustworthy. Be patient; it takes time.
Your host, Ken, is also active in a Unitarian-Universalist congregation and occasionally gives sermons there. This sermon covers the basics of mindfulness concisely. The sermon begins at 34:20. Skip the hymns; our singing is terrible!
https://www.youtube.com/watch?v=r6ZQjbvJLQw&t=2820s
In 2018 Ken, and a friend who was ordained in the Taego school of Korean Zen Buddhism, built and founded a zendo in Jenson Beach, Florida. Known as the Indian River Zendo, pictures of it follow.