Reality refers to the 53 complete worlds on Flash version and 220 complete worlds on HTML5 version within the main Candy Crush Saga game. There are 16505 levels in Reality on mobile version.
On the Flash version, there are 90 levels in World Two to World Ten, other than World One, which has 80 levels, and World Eleven and the following worlds have 45 levels. The HTML5 version, on the other hand, has 75 levels in each world (except World 1 has 65 levels).
See the full list of Reality levels.
Gallery
The reason why it is called "reality"
A layout of Reality
Reality world 1 map