It may save a lot of peoples time. If you don't want to see this FAQ regularly, please add the subject line to your kill file. This is a protection against junk mail. Part 1 is oriented towards practical usage of compression programs. Part 2 is more intended for people who want to know how compression works.
Some news readers can also take advantage of the message digest format used here.
If you know very little about data compression, read question 70 in part 2 first.