Updating running systems is a solid way to keep your laptop safe, secure and running, so it's unclear why Apple has changed the software update site again. Yes, macOS Mojave has moved System Updates from the Mac App Store to System Preferences.
The other main feature in this section of System Preferences is a checkbox labeled "Automatically Keep My Mac Updated." Enabling it will allow your system to download updates from Apple on your own without express permission. We recommend that you disable this setting so you can get full control of when major updates ̵
Earlier its own app moved the software update to the Mac App Store in 2012, where it lived under the Updates tab. Why updates have been moved to the third row of System Preferences is unclear, although it can help users to distinguish between third-party software updates and system updates issued by Apple itself.
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The movement also gives macOS another resemblance to iOS, where Software Updates are in the Settings app.
How to run system updates on macOS
1. Click the Apple logo in the upper left.
2. Select System Preferences.
3. Select software update.
4. Click Update Now if an update is available. Follow the onscreen instructions, which often include restarting the system. If you click command + R after clicking the gear icon, this page refreshes to check for updates.
If your system is up to date, you'll see the checkbox to automatically install Apple Updates and the Advanced button, which allows you to set preferences for how Mac looks after updating and installing. Henry T. Casey