Winter Challenges to warm the mind and heart.  
  HINT:  The equal signs found at the end (either one or two) tell us that this will, at least to start, be a Base64 code.  You can start simply by going to this site, entering the code into the Base64 box, and finding the resulting ASCII Text (words we can read).  But in this case that doesn't work...there's something else going on. 

Another box at that website is for ROT13 code (really this just means to rotate all the letters 13 over or halfway through the alphabet).   If you place the code below in the ROT13 box and convert, then copy the resulting ASCII text into the base 64 box (note it still has 2 equal signs), then convert that, you'll see the name of a famous reindeer.
  Santa said his favorite reindeer was a secret, so he encoded it.  
  But there's must be something we're missing!  
  Who is Santa's favorite?  DzkcqUcyot==