The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point on the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be directly overhead. Its northern equivalent is the Tropic of Cancer.
The Tropic of Capricorn is one of the five major circles of latitude that mark maps of Earth. As of 18 March 2019, its latitude is 23°26′12.5″ (or 23.43679°) south of the Equator, but it is very gradually moving northward, currently at the rate of 0.47 arcseconds, or 15 metres, per year. From Wikipedia