When you sense something, you know it intuitively, like when you can tell your mother is angry not by her words but by the tone of her voice.
Sense has many shades of meaning, all involving understanding or becoming aware of something. You can use sense to describe something perceived with your senses, like when you sense your dog is near because of the smell. Sense also refers to the unconscious process of figuring something out, like when you sense that someone is cheating at cards. If you have common sense you don't do foolish things. The sense of a word is how it's used.