First off, no one should be buyin chopped and screwed albums cuz they saw an artist of theirs released a chopped & screwed album.
Its a specific genre of rap music that originated in Houston, TX because of DJ Screw. He would slow down the record slowing the beat and the vocals, as well as chopp it up putting breaks in the song between words, as well as bringing certain phrases back so they get repeated 2-3x. DJ Screw made the music specifically because when people are "leaning" which means tripping off codeine which they drink in 2-4 oz amounts mixed with sprite or other shit. You may have heard it called lean, purple, purple stuff, drank, purple drank, chunkin a deuce or a trae in the cup - it all means the same thing. Codeine drug culture was very big in the houston drug scene in the mid to late 90s when Screw was making screw tapes and is still big today. DJ Screw gave artists such as Big Moe, Lil Flip, HAWK, Big Pokey, Z-Ro Chris Ward and countless others their big breaks. DJ Screws tapes became so popular that houston hip hop embraced the style of music. Now Houston artists - Slim Thug, Lil Flip, Big Moe, Paul Wall, Mike Jones, Z-Ro, Bun B- etc release screwed & chopped versions of all their CDs - usually done by DJ Michael Watts or DJ OG Ron C. Also, most underground houston mixtapes were released exclusively in screwed & chopped versions until recently - which is why most Lil Flip freestlyes you find on the net are screwed.
Chamillionaire was asked the following question in an interview and here is his response - great summary
Q:I read in an article you're going to release a chopped and screwed version of your CD for your fans as well as a normal one; can you explain to the readers the difference of a chopped and screwed version as opposed to a normal one?
A:The chopped & screwed version is basically a remixed & slowed down version of the songs that you would normally hear in regular speed. The tempo of the music is dramatically slowed down by a DJ and the pitch of the voices and the music changes. My DJ O.G. Ron C screws & chops all of my projects because that artform is a real big thing in the South. The world is starting to pay more attention to the style of music and it's really an acquired taste. Some people like it and some people don't but around the area where we all live that's the biggest style of music there is and that style is a main part of the reason why I am where I'm at today. R.I.P. to DJ Screw the creator of screwed music.
Personally I LOVE SCREW MUSIC - when your drunk as fuck and high as hell that shit sounds beautiful - when its done well it sounds great and most people from Houston are huge fans. So if its not for you, fine - but you gotta understand that its part of a houston hip-hop culture thats slowly spreading across the south and US. Try it out