Mac OS X: Determining Your OS Version & Update

General Information

This information has to do with the way the computer processes information and its available current features.  Newer versions are more secure and can handle newer programs more effectively.  To determine what version you are using on your Mac Operating System, follow the steps below.
 

Find Your Mac OS Version

1. Select the Apple menu icon in your taskbar, then click About this Mac.

2. Your current version information will be displayed in the pop up.
 

Update Your Mac

1. Select the Apple menu icon in your taskbar, then click System Preferences.

2. Select Software Update.

• Note: If you don't see a Software Update option in your System Preferences, use the App Store to update your Mac.
• Note: If you are on a much older version of Mac OS, please see the following article for update options: https://support.apple.com/en-us/102662

3. Click Update Now to stay on your current version, but just install the latest updates.
    OR
    Click Upgrade Now to move up to the newest available major OS update for your Mac, such as Catalina or Big Sur. This may take time to finish depending on your current installed version.

Referenced from Apple and support.apple.com