Answer and Explanation:
Uranus' spin axis being tilted at
essentially indicates that Uranus is on its side, with the poles alternately facing away and towards the Sun. This type of tilted axis is a unique feature among other planets.
Each pole remains under darkness and light for long periods of time.
Change is seasons is also such that half the planet remain in dark for one season and other in light seasons. Due to the sideways alignment of the axis of the planet to the Sun its rotation results in regular alternation of darkness and light for the another season.