A file extension is the characters after the last dot in a file name. For example, in the file name "winmail.dat", the file extension is "dat". It helps Windows select the right program to open the file.
We have a huge database of file extensions (file types). We hand pick programs that we know can open certain file types, and make them available for download on this site.
All software on File.org is either free or free trial versions of commercial software. We never charge for downloads. The same downloads are available directly from the manufacturers.