Text files are any kind of computer files which contain normal human readable material. Many other kinds of binary based files, such as program executables, encrypted files and files from programs that use binary formats to store their output, all need to be somehow tranlsated into a text format to be read by humans. The exact characters allowed in this format can vary based on which machine you use, but generally that is what ASCII is for, its a set of codes that people use to represent human understandable characters and some screen, printer and networking formating commands. Unicode is a newer standard in which you can find familiar ASCII codes as well as codes for characters in many more languages other than those using romanized characters. Therefore, while ASCII only needs 8 bits of storage, Unicode can use up to twice as much in order to handle the thousands of characters found in different languages of the world.
Copyright 2004, Daniel Heller