Birkenstock is a German shoe manufacturer headquartered in the municipality of Vettelschoß. The hallmark of Birkenstock shoes and (more commonly) sandals is the contoured cork or rubber sole that is formed to fit the contours of a generic foot. Similar to an orthopedic insert; though nowhere near as supportive.
The company can be traced back to its founder Johann Adam Birkenstock who registered the name in 1774. It was not however until 1897 that the company, under the guidance of Johanns grandson added the now iconic contoured sole.
Because of their comfort and support Birkenstocks are popular among those in the health care profession and other professions who must be on their feet for long periods of time. When worn casually (outside of work) Birkenstocks are typically worn without socks; as socks and sandals is considered to be an unfashionable combination.