Plain text files can be saved with a variety of extensions, such as .LOG, .README, and .ASC, but they usually have a ".txt" file extension. They contain unformatted text and can be opened by any text editor or word processor.
Text files are commonly used for basic text documents, but they may also serve as input and output files for various programs. For example, some programs can import data saved in a text format. Other programs export program results or log data into a plain text file. The unformatted text allows the documents to take up the smallest space possible.