Most of todays CD’s sound like garbage because they are made “hot”. “Hot” means that the CD is supposed to sound as
loud as possible on cheap sound systems. That means squashing the dynamic range of the music.

Bob Speer has written an interesting must-read article about this subject.

Low dynamic range means that the lowest and loudest part of the song are actually quite equally loud. With high dynamic range the difference between the two is much larger.
I have some examples here for you:

a song by Rammstein, released in 2006:

as you can see, almost the entire song contains clipping. this is a very bad mix. Most of todays music looks like this. And it sounds like noise. The sound has no dynamics what so ever.

But there are exceptions:

a song be Norah Jones, released in 2005

a perfect mix. This is a mix where one does take advantage of the available dynamics in the CD-format.
But back when CD was new, the mixing was different:

a song by A-ha, released in 1985:

as you can see there are no clippings, but the mix does not take advantage of the large dynamic range of the CD.