The majority of the Microsoft suite of products have these options when you are saving. Although the default options of Excel Workbook, Word Document, PowerPoint presentation etc are used most of the time these other Save As options are extremely useful in certain circumstances.
Each file type has a different file extension. The examples I will show here are for Microsoft Excel. For the standard file the extension is xlsx. This file type has been used since 2007.
Save As Macro enabled
If you have created a macro in a file it is vital that it is saved as a macro enabled file otherwise the macro will be lost. It does warn you before this happens, but you know how many times we don’t read these messages!! The file extension is xlsm.
Save As 97-2003
Many files are still stored in this format because they were originally created in these versions. For a while many files were still stored in this format to ensure everyone could open them (xlsx files could not be opened in earlier versions then 2007) but this is not normally required now as the chance you are sending them to someone with 2003 software or earlier is small. The file extension is xls.
Save As CSV (comma delimited)
CSV or comma separated value files are often created when you are exporting information from one system to another. CSV are pretty universally allowed. Although a lot of files transfer directly from one application to another CSV gives another option when required. CSV is the file extension.
Save As Template
Files saved as templates are less likely to accidentally be changed than copying and updating an existing file. They are accessed from the file menu and new once they have been saved. The file extension is xlst
Save As PDF
Saving as a PDF prevents changing of the data which can be helpful. It can stop accidental changes being made on particularly important files. The file extension is obviously PDF!! It stands for portable document format.
Save As XPS
It stands for XML paper specific and is very similar to PDF files with the extension XPS.