TwoPynts indicated that he was curious about

lossless compression

Compression of a computer file reduces the size of the file.  There are
dozens of compression methods.  For each of these, there is also a
decompression method. 

The most important attribute of a compression method is 'loss'. 

Compression and loss do not always go hand in hand. 

1. A 'lossless compression' method does not loose any of the information
   that was present in the original file. 

e.g. the PKZIP program uses lossless compression methods.  GIF, PSD
and PNG are non-lossy compression formats. 

2. By contrast [BTW, would this use of the term 'contrast' create a puntax
   liability for me?], a 'lossy compression' method does not preserve all of the
   original information -- only just enough to fool you into thinking you got
   back what you started with.  Some of these lossy compression methods
   have (allow) varying degrees of 'loss' ... some implementations allow you
   to choose how much loss ... i.e. how much quality -- some implementations
   assume that we're just too dumb to know what to do and don't allow us a
   choice.  Some marketing types prefer to spread confusion instead of straight
   answers. 

e.g. JPEG and MP3 are always lossy methods.  How much loss?  Well, that depends ...

TwoPynts also guessed that

looks at the image data and when there are patches of pixels that
have the same

... yes, that is an aproximate description of compression methods in general. 

I had to laugh when TwoPynts said,

Though I am a total noob

and

at least until one of you good people shoot it down, hahahah.

... because he did a pretty good job of tricking us into explaining it.  LOL

--
Martin