Export means using File>Import and Export. It doesn't matter where the
resultant file goes.
Best practice for what operation?
File>Open>Outlook Data File
Backup means nothing more than making another copy of your PST for
safekeeping by some means, without actually specifying those means.
Exporting is not the best way because information can be lost in the export
process. Yes, just copy the PST to another location, making sure Outlook is
closed when you do. The tool PFBACKUP from Microsoft can help automate this
process to a degree.