Compression

Lossless vs Lossy

This is not specific to images and what these mean can differ from medium to medium(eg. music vs image)

With music MP3 actually throws out parts of the music people typically can’t hear. That part is gone forever.

Lossless compression is like you taking a ball, and letting the air out.
You can put air back in and it’s the same ball.
You just look for patterns of 1’s and 0’s A’s replace them with something shorter.