Orthotics are customized shoe inserts which are designed to assist in correcting balance and alignment problems of the foot and ankle. Orthotics can also play a role in reducing strain on one's knees and back. They may also be used to correct limb-length discrepancies. By helping to restore alignment, orthotics can minimize the stresses to bones, cartilage, tendons, and muscles, making weight bearing and gait more comfortable.

Orthotics can also be used to simply diminish the amount of pressure received by different areas on the bottoms of the feet. Specialized, softer materials are often used for diabetic patients who are at risk for developing ulcers due to pressure. Padding is also used to minimize callus buildup, for those who experience this routinely.

Orthotics are made to each individual's feet, and come as a pair. Orthotics can be made in all shapes and sizes, and can be customized to what one wears, on a daily basis. Orthotics can be made for sneakers, cleats, work boots, ski boots, women's and men's dress flats, and high heels. There are even orthotics which are created for some sandals, such as Birkenstocks.

It should be noted that except for their use by children, orthotics will not have a long-term "corrective" effect on structural abnormalities (ie: when stepping out of an orthotic, a flat foot will remain flat). Even in children, the total "corrective" ability will be limited, to a degree. They are used to address the symptoms associated with acute problems, and as a preventative measure, against the development of future problems.