What are CBZ files? CBZ files are zipped file archives that have had their extension renamed from .zip to .cbz

What are CBR files? CBR files are rarred file archives with their ectension changed from .rar to .cbr

The idea behind this is that comics are other graphical books are usually scanned as JPEG files and combining them into a compressed zip (or .rar) file is a convenient way to package the images together. This has advantages over creating a PDF file - mostly b/c the format is open and PDF is closed so it's more flexible. There are several programs out on the net to view these files. Here are the most popular ones:

CDisplay Sequential Image Viewer
Comical
BdzExplorer

and my personal favorite: GonVisor - this program has a lot more features and can create cbz and cbr files and also extract the images from your files.

Screenshot:

More info at Mutant Liberation Front