BB cream stands for either Beauty Balm or Blemish Balm - it originated as a cream with light coverage to protect skin after cosmetic/surgical procedures, then was developed in Korea. The true BB creams have qualities have light coverage and other benefits such as hydration, sun protection, etc. but many of the Western formulations are basically just tinted moisturisers, particularly the cheapest ones. They are still perfectly good products, but there is essentially very little difference.
CC stands for Colour Correcting, so many are made with different pigments to counteract discolouration in the skin, e.g. green tint for redness. Again, though, most high street ones are tinted moisturisers, e.g. the Bourjois one (which is lovely but just a slightly peachy-toned TM).
I am 
about DD and even EE creams! They are largely marketing based imo.