A PSA Backup file is really just a ZIP file with a specific internal structure in it.  It will contain everything needed to completely recreate your website on any server.
This includes:
Website Files
SQL Server Database BAK Backup
Email addresses
FTP accounts

Your website files will be located in the domainname\httpdocs folder.  Your database BAK backup will be in the root of the backup and will have no extension.

If you'd like to extract files out of the backup, just use a program like WinZIP or WinRAR to open the file.