The answers above are a little bit confused....
The quick answer is that on a new PC, you may get one two to large updates at first and a small number of smaller ones. If you have other MS products installed. they may get numerous updates.
The situation is:
Windows 10 updates are "cumulative updates". Cumulative updates (CUs) include all of the content of earlier updates for that version of windows. That means that in order to bring "Windows 10" up to date you need to download just the latest update.
Easy eh?? OK no... That statement sets the flavour of what happens but It's a bit more complicated than that.
As with anything, the devil is in the detail, and above I used the words "Version" and "Windows" to qualify the statement.
Let's deal with "version" first...
Windows 10 has new versions released relatively frequently (once or twice a year for ordinary users). These new builds are where new features and major changes are introduced. The "Anniversary update" is one of those. These big releases are more correctly known as upgrades and also each one also goes by other names - the Anniversary update has a project name of "Redstone" or "Redstone 1" and a version number of 1607 (released in year 16, month 07). Upgrades are generally large to download, take longer to install, and as mentioned above will introduce functionality changes. Upgrades will contain all the updates that were releases to earlier versions and are relevant to the new version.
The cumulative updates for Windows are based on the Windows 10 VERSION installed and contain all updates since that version was released. These come out frequently - At least one a month, sometimes more frequently. As you can imagine the physical size of a CU increases across the life of a upgrade but only the content needed to install the changes between 'what you had' and 'what is current' are installed when you install a CU.
So.... When updates (even on a new PC) are detected you will probably see just One update for Windows. This may be a version upgrade or a cumulative update, but it may be a be a big one and if it is a version upgrade you may get a CU immediately afterwards.
So just one update - great eh??? No, that’s there the qualifier "Windows" that I used above comes in...
The updates above keep the underlying Windows OS updated. There may be other things that need updating as well. "Abobe Flashplayer" is a separate stream of small updates which MS frequently push out, Other Microsoft components such as ".NET" runtimes also have separate update streams, as do other MS products (Older and come current versions of Office etc). Some of those different product updates are cumulative (.net) and others discrete (and possibly numerous) older office versions).
Putting all of that together..At any point you may be offered one ore more of:
- A Windows version upgrade
- A Windows Cumulative update
- A .net cumulative update for each version of .net framework installed
- A flashplayer update
- The MS malicious software removal tool
- Sundry updates for other MS Products - These may be numerous, depending on the products.
That is still better than the hundreds of updates you might have experienced on older OS's. First time, the Cumulative updates may take a time to download, but again timewise much better timewise and quantity wise than before.
[Edited to add: The above discussion is based on the normal end-user update path that most Windows users are on - the so called "Current Build". Other tracks for business and beta testers ("insiders") exist. They do similar sorts of things but a different paces]
Edited by x64, 14 January 2017 - 03:03 AM.