In 1972, the U.S. proclaimed a contiguous zone extending from 3 to 12 miles offshore (Department of State Public Notice 358, 37 Fed. Reg. 11906 (June 15, 1972), consistent with the 1958 UN Convention on the Territorial Sea and Contiguous Zone.
The aperture of a lens is the opening in the diaphragm that controls how much light is allowed to reach your focal plane (film or sensor). The aperture is usually rated as a fraction of the focal length, hence the f/x.y nomenclature. The wider an aperture is, the more light it allows through, and the smaller the number under f/ is.
Yep you've got the abbreviations right. Av = aperture value = aperture priority auto exposure Tv = time value = shutter priority auto exposure Both of these modes allows you to set a firm value for either aperture or shutter speed, and let the camera work out the exposure needed.