The way I see it, there are two basic forms of meditation.
I think of them as '0' meditation, and '1' meditation.
The first is a way to relax your mind. You don't go to sleep, but relax, and let your mind stop thinking.
Try it: whenever your mind has a thought, you just let it go.
There are many ideas on why this is good for you. I like to just think that it gives your brain/mind a break from its normal thought processes, but a different kind of break than sleep gives you.
Persist a little!
The second kind of meditation is where you focus your mind on one thing to the exclusion of others. You keep passing thoughts from playing out by focusing on one single thing.
That thing can be a symbol, chant/verse or it can be your breathing cycle, or drum beat.
One of the best ways for me to meditate is to just sit and empty my mind, and say 'inhale' inwardly whilst inhaling, then say 'exhale' silently whilst exhaling.
Again, persist a little.
It gives your brain/mind a rest. There is piles and piles of optional culture and stuff built on top of it, but I reckon meditation boils down to one of these approaches.
Final note: Your body doesn't have to be stationary, but it can be!