A PST file, or Personal Storage Table file, is a file used by the Microsoft Outlook email client to store emails, contacts, calendar entries, and other data related to your email account. PST files are important because they contain important information about your email account and allow you to access your messages and other data even when you are not connected to the internet. However, PST files can become corrupted or damaged over time, so it is essential to back up these files regularly to ensure that all your data remains accessible. Additionally, it is a good idea to use an antivirus program or other security software to protect your PST files from malicious software and viruses that could potentially corrupt or damage them.