Supposedly you want to get all email addresses in some folder, e.g. because you want to send an email to all of them. Now, there is a way to do this in Outlook by exporting a folder to Excel. But this way has some limitations (such as it does not export IMAP folders).
If you want to export all your contacts from Outlook as vCards you find that there is no easy way to do this in Outlook. A solution is to use a software such as vCard ImportExport, which simplifies the export task to just few button clicks.
The reason why vCard file format is so useful is that one file can hold all your address book contacts. But how to merge multiple vCard files to one? The easiest way is to use some software such as vCard ImportExport, but there is another way without using any software, but windows command line interface.