"Be Still" means: STOP whatever you're doing right now, take a deep conscious breath, be aware of your surroundings, clear off your mind, and be at peace.
I made this to remind me, so that each time I look at it I will take a short break from whatever I am doing, and thank God for this beautiful wonderful moment.
This is part of the phrase “Be still, and know that I am God” (Psalm 46:10).
It simply means, if you are still, as in simply taking/accepting the present moment as it is, at that moment, you will find peace, wherever and whenever you are.
I only understand this after I read the book 'A New Earth' by Eckhart Toole. In fact, the book made me understand a lot of things that Jesus said.
Go read it. If I say anything more it'll just be a repeat.