When you think of the word surround, think of something that's around you on all sides, like the trees that surround you in a forest or the people who surround you on a city street at rush hour.
Sometimes surround describes the position of troops that force the enemy to surrender. You can also surround your property with a fence, or surround yourself with positive people. Both of these offer a way to protect or strengthen the thing in the middle — your house or your well-being. In a movie theater that has "surround sound," the audience feels like it is in the middle of the action because of the speakers placed all around the space.