Like earlier versions of the operating system, Windows 8 can check to see if software updates for your computer are available from Microsoft— and then install them for you so you don't have to remember to do it yourself. Security updates and other software patches deemed important or critical are typically installed automatically when Microsoft pushes them out. (The company often releases the updates on the second Tuesday of each month, but it can happen as needed).
But even if you have the automatic updates option turned on, not all the software Microsoft sends you will install itself. Certain types of updates, including fresh versions of programs that have new user agreements or terms of service statements, require your attention because you are asked to read the legal fine print — or at least click the Agree button — before you can install the software.
Some updates, like feature enhancements or updated device drivers, are considered optional and not critical to a program's ability to function. When an optional update is ready, you usually get an alert that it is available if you want it, and Windows leaves it to you to do the installation yourself.