The most simple definition of mindfulness I find is from the Mirriam-Webster Dictionary:
1. the quality or state of being conscious or aware of something.
"their mindfulness of the wider cinematic tradition"
2. a mental state achieved by focusing one's awareness on the present moment, while calmly acknowledging and accepting one's feelings, thoughts, and bodily sensations, used as a therapeutic technique.
What is the benefit? Being mindful allows me to remain present. It is in the present I find happiness. In the present I am free from worry, anxiety, and other emotions that disrupt my joy.
This is Max.
The past few days have been out of routine. We haven't had as much time together as I like. This morning he climbed in bed beside me and put his head on the pillow. He was simply present with me. Then I pet him. It was then I saw Max in Mindfulness. He lifted his head and fully enjoyed being pet. He wasn't thinking about the squirrel he likes to chase in the yard; his food and water bowls; he wasn't resentful that I'd been away more than usual. He was in the moment, simply enjoying being pet.
I strive to be more like Max.