This article is from the Go FAQ, by Morten PAHLE email@example.com with numerous contributions by others.
All these are various file formats used to record a game of Go.
Recently, the Smart Game Format (.sgf files) has become the most used
format, and it is also the most frequently used format on the go
Look at section 6.1 for information on how to find editors.
If you are interested in writing an SGF editor, or you want to know
more about the development of the format and its possibilities, take a
look at <http://www.red-bean.com/sgf/>.
The sgf format is also often used to post positions to the newsgroup.
Jan VAN DER STEEN has a tool on his web site which will translate an
SGF file to ascii diagrams, .gif files or postscript files: