What is the SIHClient.exe?

Seems like SIH is for "Silent Install Helper". It starts background installation of Windows updates, as planned in advanced update options.

> Seems like SIH is for "Silent Install Helper". It starts background installation of Windows updates, as planned in advanced update options.

Unfortunately, as other have noted, this answer is not correct. It is not what Windows itself is saying about the file.

SIH appears to stand for : 'Service Initiated Healing' Client, NOT 'Silent Install Helper'

See kennyz93's comment on Technet about this same question :
https://social.technet.microsoft.com/Forums/en-US/6055943e-451b-4510-b696-3d7b3969bb64/what-is-the-windows-10-system32-file-sihclientexe-?forum=win10itprogeneral

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> I find running FSUTIL handy at times like this. See below .. this is the Service Initiated Healing client .. not the Silent Install Helper client.
C:\>fsutil hardlink list c:\windows\system32\SIHClient.exe
\Windows\System32\SIHClient.exe
\Windows\WinSxS\amd64_serviceinitiatedhealing-client_31bf3856ad364e35_10.0.10586.0_none_a963ed1670926cb8\SIHClient.exe
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=> I find the same on my own system (the minor version number has changed since), and you can confirm this on yours just the same.

Also see Jo Mei  even more detailed answer on :
https://www.tenforums.com/general-support/17135-file-browse-dialog-showing-limited-results-compared-explorer-window.html

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> The OS itself gives the answer. Run the Task Scheduler with the command %windir%\system32\taskschd.msc /s

In the left Tree View navigate to: Task Scheduler (Local) -> Task Scheduler Library -> Microsoft -> Windows -> Windows Update (see Screenshot).

Click the Task named sih and there's an explanation:
This daily task launches the SIH client (server-initiated healing) to detect and fix system components that are vital to automatic updating of Windows and Microsoft software installed on the machine. This task can go online, evaluate applicability of healing actions, download necessary payloads to execute the actions, and execute healing actions.
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Regards.