The human brain has two default modes of operation and you have very little control over them. They exist because they offered an evolutionary advantage in much more dangerous times, but don't necessarily promote a sense of well being/happiness in a modern relatively safe world. a) Pleasure seeking and pain avoidance b)Self referential thought ("Am I good enough, smart enough and do people like me?")
Mindfulness offers a third option. Relaxed open awareness with general acceptance. It can be done my anchoring awareness on a physical sensation like the breath. You won't be able to hold your concentration there very long before you realize you're thinking of something else. You are mindful when you realize your mind had drifted and you bring it back to your anchor.
It offers tons of well studied and documented benefits like increased activity in the left prefrontal cortex with is good for reasons that google can tell you.
A note from my experience. Expect the timeline of benefits to be similar to starting a cardio or weight training program. Your first few times may seem like a waste of time but the benefits start piling up after a few weeks.