PST file (personal storage file) is a backup file for Outlook database to stores all type of emails, contacts, calendars, tasks, notes, etc from the MS Outlook email client. You can use this PST file to export Outlook mailboxes to other email clients and services including Gmail.
Outlook to Gmail Migration Tool helps you in easily export pst file data to your Gmail account. This software quickly scans the pst file and restores all Outlook components, then you can use your Gmail username and App Password to import all data to your email account. This Gmail Migration Tool for Outlook can also migrate PST to G Suite account.
More Info- Migrate Outlook to Gmail