This will only relate to Windows systems.
The first two are the types of update that most people will consider.
Operating system patches.
I have Windows set to download the patches as they become available and notify me. I then usually install within the next couple of days.
This is set to download and install automatically. The Avast software I use checks every 4 hours to see if there are updates available.
Even if you think your Windows system is up to date, it might be worth a check, it only takes a minute.