If you want to back up everything in Outlook then as VoG has already indicated you should back-up the .pst file.
Don't realy know why you were recommended the comma separated values optionas this is an option on Exporting Outlook data. This is a format used to transfer data between disparate applications and would only be useful if you wanted to take the Outlook data and use it in some other program. Given you asked for advice on backing up everything in Outlook, which would include emails, contacts, task lists, etc then you would have a very large csv file and making a copy of the .pst is the better option.
If you want to export a contact list for example then you can consider File - Import and Export - Export and in here you will find the comma separated values (Windows) option.
Sounds a good choice to go with the .pst if your disk is likely to fail.
An example of exporting data from Outlook to another program would be if you wanted to get all your contact's details into Excel so you could manipulate the details and/or sort in different ways. You may also want to import your contacts into another Address Book, not Outlook.
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