A side may also mean a part of something. For example, on a humanbody, the right side means the parts of the body that make up the right half of the body.
Inside and outside are terms use to show where something is. If something is inside, it is in something, for example: "The cookies are inside of the container." means that the cookies are in the container. The area within the canister is the inside of the canister. The outside is the area not in the canister. Outside is the opposite of inside.