Everything on a computer is stored in a file and there are only two basic types of files.
The first is a file that you can Open and View – a ‘Document’ like a Spreadsheet or a Letter. They don’t do anything. They are just something that can be looked at, altered and printed.
The other type of file is ‘executable’. It does things and is Run rather than Viewed. This type of file can damage your computer so one needs to be careful when using these.
Software (e.g. programs that allow one to open and view the other type of file) are executable files. Some documents have executable content in them (often called Macros) so it is important to be careful of these files as well.