What's a File Extension?
A file name consists of two parts: before the dot and after the dot. We usually call the part before the dot File Name, while File Name Extension after the dot. If the there are more than one dot, the last dot takes effects.
The file extension indicates what type of file it is. For example, filename.docx is a Microsoft Word document. Similarly, you can tell file.jpg is an image file and readme.txt is a text document. When you double click on a file, the file extension determinates what program will be used to open it. This is why you should be careful to change the file extensions, which would probably result in failure to open the file.
Most file name extensions contain 3 characters, but in fact, fewer or more are also valid and popular. For example, .c (C source code file), .db (database file), .gz (compressed file), .torrent, .gadget (executable file), .mswmm (Microsoft Windows Movie Maker project file), .msproducer ( Microsoft Producer project), etc. However, the 8.3 filenames have at most eight characters, optionally followed by a period "." and a file extension of at most three characters. It's most used in the old versions of DOS.
There are thousands of file extensions that are created by software and accordingly need thousands of program to open and edit those files. There is no need to remember them because you cann't, but you should learn about the common file formats to fix programs quickly when there is one in the way.
Below is the daily use file extensions. See more common file types.
