Soak Up The Sun

When you add heat to things, they change their temperature! This is not just correlation. It's a statement of cause-and-effect loosely expressing the First Law of Thermodynamics:

Heat in minus heat out equals change in heat

— it's not just a suggestion ... it's the Law!

Earth, like most planets, receives virtually all its incoming heat by absorbing radiation that was emitted by the Sun. 

If sunshine was the whole story, Earth would get hotter and hotter without bound (see the Law above). Eventually, our planet would melt, then boil, then vaporize! Of course that hasn't happened in all these billions of years because heat is also emitted by our planet back to space. The rate of thermal emission  (infrared radiation) by the Earth has to exactly balance the global average rate of absorbed sunshine. If it gets out of balance even a tiny bit, the world heats up or cools down to re-establish the balance. This is the only way climate can change!

The Sun is (thankfully) a pretty constant emitted of heat radiation. But of course sunshine is not evenly distributed across our world. There's no sunshine at night. Because of the tilt of Earth's axis, sunshine varies by season. Away from the Equator, the days are shorter and the Sun is lower in the sky during winter than during summer. At the Equator, the days are always 12 hours long and the Sun crosses almost directly from east to west all year, shining straight down at noon.

Over the course of a year, the tropics absorb more sunshine than they emit back to space as infrared radiation. Conversely the poles emit more than they absorb. According to eh First Law of Thermodynamics above, this means the tropics should get hotter and hotter and the poles should get colder and colder. FOREVER!  Clearly that's not the case. It gets cold in the polar dark, but not infinitely cold. And the tropics can be uncomfortably hot, but not infinitely so.  

The Equator-to-Pole difference in climate is finite because of heat transport by the atmosphere (winds) and oceans (currents). Buoyant hot air rises in the tropics and flows toward the poles, carrying its heat with it. Denser cold air sinks at the poles and flows back toward the Equator in both hemispheres. Similarly the five great Gyres in each  subtropical ocean basin feature poleward-flowing warm water and Equatorward-flowing cold water that equalize the heat. 

Every warm breeze and frozen gale, every drop of rain and flake of snow, every little ripple or big wave or mighty ocean current -- all are driven by the excess of tropical sunshine and the polar darkness. These flows of air and water contribute greatly to making the Earth the lovely habitable planet it is.