The Tropic of Cancer lies at 23d 26' 22" (23.4394 degrees) north of the Equator and marks the most northerly latitude at which the sun can appear directly overhead at noon.
This event occurs at the June solstice, when the northern hemisphere is tilted towards the sun to its maximum extent.
1934 first edition of Henry Miller's Tropic of Cancer
illustrated by Maurice Kahane
The Earth's tropical zone ("the tropics") includes everything between the Tropic of Cancer and the Tropic of Capricorn.