If you are scared of someone or something, you are frightened of them.
I'm certainly not scared of him.
我当然不怕他。
I was too scared to move.
我吓得动弹不得。
If you are scared that something unpleasant might happen, you are nervous and worried because you think that it might happen.
I was scared that I might be sick.
我担心我可能病了。