When using open source files, you will notice that the format of these files are different to any other program. This is because it is particularly used for open source software. However, individuals who are using open source and Microsoft on an ongoing basis will also know that the files can be opened in both applications.
The compatibility of this allows individuals to change, edit and add to your files through both applications of your choice. The standard format at the end of the file is ODF, which indicates it is an open document file format compared to the DOC format found in Microsoft. This is probably the biggest difference and should not hinder individuals from using open source programs.