There are an enormous number of uses of both of these words. The meaning comes from the context.
Grab me a loaf bread, could you? (From the shelf in a store. Use your hand to put it in my cart.)
The thief grabbed my phone right out of my hand.
Don’t grab. Wait your turn. (A parent to his child at the dinner table. Here, it’s a negative.)
Let’s grab lunch.
I’ll drive . You grab some sleep.
He took my car. (Could mean that he stole it. Could mean that he used it.)