At level 51 I saw this owl icon in the top right of my I-phone, and when I click on the owl I got a whole other set of levels to play beginning with Level 1 'Sleepy Slopes' then 'Funky Factory'. What is this new set of levels?
The new set of levels is called "Dreamworld". It was released in December 2013, but only becomes available after you've beaten level 51. (since many folks who play regularly had already beaten 51, they probably thing it was just released to everyone).
It is a nearly identical set of levels to the first 65 levels in Candy Crush, with a few distinct differences:
Levels are the exact same layout, but some may have more possible candy colors than the original version.
Timed levels do no exist in Dreamworld. They were replaced by regular "Moves" levels.
The new character "Odus the Owl" appears on the Moon Scale in each level. The Moon Scale keeps track of two colors of candies and each candy you crush of one of those colors will make it tip one way or the other.
After a set number of turns, a "Moonstruck" even will occur. This event will destroy one or more colors of candies, and it will prevent those colors from respawning for the duration of the event. The Moon Scale is also permanently fixed during a Moonstruck even, so you can't fail from Odus falling, until it is over.
If you are interested in further details I wrote an article about Dreamworld tips and tricks here.
It is not on level 51 where you get this, it was implemented in December 2013 i believe. It is just candy crush on a different world. The owl "named Odus" himself adds some new mechanics where you have to match certain candies for bonuses, you actually have to balance him and matching the candies on both sides of the scale. When the meter is full you get a moonstruck if at that time the scale hinches to the side it will remove two candy types, if it is balanced only one type. It adds some extra elements to the regular game.