Answer:
Latitudinal lines are imaginary lines wrapping around the Earth. There are five main lines and since they are parallel to each other they are called the parallels. The central parallel is called the equator and it splits the planet into two hemispheres, northern and southern. The equator has the latitude of 0°. Next main parallels are at roughly 23°, both northward and southward. At 23° N (north) is the Tropic of Cancer and at 23° S (south) is the Tropic of Capricorn. Finally, at roughly 66°, both north and south, there are last two main parallels; at 66° N there is the Arctic Circle and its southern counterpart is Antarctic Circle at 66° S.
Roughly speaking, these lines are the limits of three main climate zones of the Earth. Climate zones are belt-shaped regions between the parallels with clearly distinctive climate features. So, between the Tropic of Cancer and the Tropic of Capricorn, there is the tropical zone. Between the Tropic of Cancer and the Arctic Circle in the north and the Tropic of Capricorn and the Antarctic Circle in the south, there is a temperate zone. And finally, between the Arctic zone and the North Pole and the Antarctic Circle and the South Pole there is polar zone.
So, to summarize, the left part of the diagram (climate zones), from top to bottom, should write:
polar
temperate
tropical
temperate
polar
The right side of the diagram (latitudinal lines), from top to bottom, should write:
Arctic Circle
Tropic of Cancer
Tropic of Capricorn
Antarctic Circle
