Why You Should Install Recommended Software Updates on Your Mac
By default, your Mac checks with the mothership (Apple) once per week to look for any new or updated software for your Mac. If there is, your Mac informs you that a new Software Update is available and asks whether you’d like to install it. In almost all cases, you do. Apple issues Software Updates to fix newly discovered security concerns, to fix serious bugs in macOS, or to fix bugs in or add functionality to Apple applications.
You can perform this check manually by opening the App Store app and displaying its Updates tab. If any updates are available, you’ll see them here.
Use the App Store System Preferences pane to disable automatic checking completely, and/or instruct your Mac to automatically download and install updates.
Once in a blue moon, one of these Software Updates has an unintended side effect; while fixing one problem, it introduces a different problem. Apple is generally pretty careful, and this doesn’t happen very often, but if you want to be safe, don’t install a Software Update until you visit Macworld, The Mac Observer, or other authoritative site and look at what they have to say about the update you have in mind.
If there are widespread issues with a particular Software Update, sites like these will have the most comprehensive coverage (and possible workarounds).
Apps need updates, too. So make a habit of launching the Mac App Store application now and then, clicking the Updates tab, and then updating any apps that require it.
Many third-party programs, including Microsoft Office and most Adobe products, use their own update-checking mechanism. Check and make sure that you have yours enabled. Many third-party apps offer a Check for Updates option in the Help (or other) menu or as a preference in their Preferences window.
One last thing: If you see a little number on the App Store icon in the Dock, you have that many updates waiting. Launch the Mac App Store, and click the Updates tab.