When you go to download SQL Server cumulative updates the options can be pretty baffling. Which file(s) do you need? Here’s some help.
For example, if you go to SQL Server 2014 CU1 you are offered these files:
There’s no explanation on the page but presumably it’s explained somewhere. It is, but it’s not easy to find. I asked on the MSDN forum and was pointed to this page which explains it quite clearly.