https://blogs.technet.microsoft.com/windowsitpro/2016/08/15/further-simplifying-servicing-model-for-windows-7-and-windows-8-1/
"Monthly Rollup
From October 2016 onwards, Windows will release a single Monthly Rollup
that addresses both security issues and reliability issues in a single
update. The Monthly Rollup will be published to Windows Update (WU), WSUS,
SCCM, and the Microsoft Update Catalog. Each month’s rollup will supersede
the previous month’s rollup, so there will always be only one update
required for your Windows PCs to get current. i.e. a Monthly Rollup in
October 2016 will include all updates for October, while November 2016 will
include October and November updates, and so on. Devices that have this
rollup installed from Windows Update or WSUS will utilize express packages,
keeping the monthly download size small.
Security-only updates
Also from October 2016 onwards, Windows will release a single Security-only
update. This update collects all of the security patches for that month
into a single update. Unlike the Monthly Rollup, the Security-only update
will only include new security patches that are released for that month.
Individual patches will no longer be available. The Security-only update
will be available to download and deploy from WSUS, SCCM, and the Microsoft
Update Catalog. Windows Update will publish only the Monthly Rollup – the
Security-only update will not be published to Windows Update. The
security-only update will allow enterprises to download as small of an
update as possible while still maintaining more secure devices."