What are the differences between sinus and fistula?

Sinus:-

Sinuses are air pockets that are located within the bones of the skull and face and are connected to your nasal passages by small tubes or channels, the stomatal complex. These channels permit air to flow from the nose into the sinuses and allow drainage of mucous from each sinus into the nose.

Fistula:-

A fistula is an abnormal connection between two body parts, such as an organ or blood vessel and another structure. Fistulas are usually the result of an injury or surgery. Infection or inflammation can also cause a fistula to form. Fistula laser treatment in Chandigarh