I lived in a Zen Buddhist temple for awhile. During that time I like to think I learned a little bit about what meditation really is and how it can be practiced. The thing people often misunderstand is that you do not just sit quietly, it's takes a great deal of mental energy to remain focused. You are supposed to focus your attention on your breathing, over and over and over again. Every time you have a thought, which is constantly at first, you must recognize it and then return your focus to your breathing. It's excruciating.
We practiced this 10 hours a day, every day. Silent sitting meditation with the midday meal taken in the meditation room in silence. Often I found myself exhausted and unable to practice and I would let my mind wander. But that's not meditation, that's day dreaming.
And all that focusing on your breathing, that's just all the whitebelt work. What you REALLY want is to get to the point, after years of practice, to be able to focus on nothing and maintain that state. THAT is true meditation. When you can allow you mind to come to rest. No thoughts invade or distract, your mind is like a placid lake, still and motionless. Only then are you truly meditating. However that takes many years of dedicated practice. So much practice that very few people ever make it there. That is the black belt of meditation, and that's when the true journey begins.
I'd love to say that I can sit quietly and allow my mind to come to rest, but I cant. I never put in enough reps, I gave up.
That's not to say that sitting quietly and trying to calm your mind isn't good for you, it is! If you can find an app on your phone that helps, great! I'm sure that will help you. Just recognize that when you are doing that, all you're really doing is learning to shrimp.
When you see those guys in the orange robes just sitting there and you wonder what they are thinking about... it's nothing. Their mind is idle and at rest. They are not thinking they are hungry, or tired, or whatever. They have learned to allow their mind to become completely still. It is a huge accomplishment to get to that point, but it only comes from incredibly dedication.