An extra depth shoe means the shoe has more depth to it so that your foot sits further down into the shoe than a regular shoe.
In an extra depth shoe your foot or feet go further into the shoe than they would in a regular depth shoe.
Extra depth shoes give your foot more room and adequate room for a custom orthotic or diabetic insole.
When you're diabetic your doctor may prescribe you some extra depth shoes or even if you have other foot conditions that require an extra depth shoe.
The extra depth shoe would make your feet more comfortable when you have diabetes or other foot conditions.
A doctor will need to fit the extra depth shoe or diabetic shoe to your foot or it could cause other health issues.
Extra depth shoes offer added volume in the shoe to accommodate for orthotics or foot conditions that need extra room.