Can you explain what a deviated septum is?

See below. The nasal septum is the bone and cartilage partition which divides the nose into two sides. When it is crooked and not in the middle of the nasal cavity, it is deviating to one side or the other. The term most commonly used to describe this is deviated septum.
Bent Nasal Divider. The nasal septum is the wall that divides the nose into two nasal cavities. The septum can become "deviated" from simply grow that way or trauma to nose which can "crack" the septal cartilage +/- septal bone, and make it "bend" more into one side more. In some cases it can bend more to one side in the front, and more to the other side in the back. Breathing becomes harder on the narrow side(s).
Deviated septum. A deviated septum is not an uncommon problem. It describes a situation when the cartilagenous/bony wall that divides the two nostrils is not midline. It can lead to nasal obstruction, snoring & even sinus issues. You only need surgery if you are having symptoms.Be sure to have your nose evaluated by a board certified otolaryngologist.
Deviated septum. A deviated septum is deviation of the nasal septum (the wall dividing the left and right sides of the nasal interior). Occasionally, deviated septum may be associated with sinus infections or nosebleeds. Septoplasty is indicated in patients with deviated septums and nasal obstruction not corrected with mediations.
Crooked septum. A deviated septum is when the dividing cartilage inside the nose is not exactly in the middle. This can often obstruct the airflow on the side its bent towards making it more difficult to breath. This can occur naturally or can be caused by trauma when you break your nose.