File Extension Library - What is a File Extension?

Want to know what a file extension is? File extensions are the short suffixes that appear after the filename. They are used to indicate the file type. In their early use, file extensions were used to indicate the generic type of a file. For example, .txt was used for a text file, and file extension .gfx for a graphics file. However, over time, file extensions have become connected with certain programs or even versions of that program.