What exactly does sfc /scannow do?

With all the tweaking that is needed with Win7, is there anything sfc /scannow could change, that I do not want changed?

I got a bit suspicious, when I ran it, because the log file is about a mile long....

Thanks for your answers...

 

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Thank you, but....

I have seen the logfile (attached) and it contains over 1000 lines like these:
0: Move File: Source = [l:192{96}]"\SystemRoot\WinSxS\Temp\PendingRenames\f96bf00d0ed5d401620a0000340de00e._0000000000000000.cdf-ms", Destination = [l:104{52}]"\SystemRoot\WinSxS\FileMaps\_0000000000000000.cdf-ms"
1: Move File: Source = [l:162{81}]"\SystemRoot\WinSxS\Temp\PendingRenames\f96bf00d0ed5d401630a0000340de00e.$$.cdf-ms", Destination = [l:74{37}]"\SystemRoot\WinSxS\FileMaps\$$.cdf-ms"
2: Move File: Source = [l:216{108}]"\SystemRoot\WinSxS\Temp\PendingRenames\f96bf00d0ed5d401640a0000340de00e.$$_resources_fbee56ab048ab239.cdf-ms", Destination = [l:128{64}]"\SystemRoot\WinSxS\FileMaps\$$_resources_fbee56ab048ab239.cdf-ms"
3: Move File: Source = [l:260{130}]"\SystemRoot\WinSxS\Temp\PendingRenames\f96bf00d0ed5d401650a0000340de00e.$$_resources_ease_of_access_themes_e29108c7f81ea04c.cdf-ms", Destination = [l:172{86}]"\SystemRoot\WinSxS\FileMaps\$$_resources_ease_of_access_themes_e29108c7f81ea04c.cdf-ms"
4: Move File: Source = [l:214{107}]"\SystemRoot\WinSxS\Temp\PendingRenames\7af1f90d0ed5d401660a0000340de00e.$$_system32_21f9a9c4a2f8b514.cdf-ms", Destination = [l:126{63}]"\SystemRoot\WinSxS\FileMaps\$$_system32_21f9a9c4a2f8b514.cdf-ms"
5: Move File: Source = [l:242{121}]"\SystemRoot\WinSxS\Temp\PendingRenames\da52fc0d0ed5d401670a0000340de00e.$$_system32_wdi_perftrack_e5904ddd3f58b556.cdf-ms", Destination = [l:154{77}]"\SystemRoot\WinSxS\FileMaps\$$_system32_wdi_perftrack_e5904ddd3f58b556.cdf-ms"
6: Move File: Source = [l:256{128}]"\SystemRoot\WinSxS\Temp\PendingRenames\da52fc0d0ed5d401680a0000340de00e.$$_system32_wdi_perftrack_traces_0af2b48360b94cec.cdf-ms", Destination = [l:168{84}]"\SystemRoot\WinSxS\FileMaps\$$_system32_wdi_perftrack_traces_0af2b48360b94cec.cdf-ms"
7: Move File: Source = [l:216{108}]"\SystemRoot\WinSxS\Temp\PendingRenames\bc39080e0ed5d401690a0000340de00e.$$_servicing_fc2045b9046cc796.cdf-ms", Destination = [l:128{64}]"\SystemRoot\WinSxS\FileMaps\$$_servicing_fc2045b9046cc796.cdf-ms"
8: Move File:
2019-03-08 02:49:04, Info CSI Source = [l:234{117}]"\SystemRoot\WinSxS\Temp\PendingRenames\bc39080e0ed5d4016a0a0000340de00e.$$_servicing_editions_596ea20ddafb9f7d.cdf-ms", Destination = [l:146{73}]"\SystemRoot\WinSxS\FileMaps\$$_servicing_editions_596ea20ddafb9f7d.cdf-ms"

and none of these tells me what I want to know, which is.... Can sfc change anything that I do not want to be changed?

 

Yes, I understand that. That is why I did not ask that.
I still think, the question I asked is pretty clear: Can sfc change anything that I do not want to be changed? Yes or No?

 

Thank you....

 

Well, there are few things,f.e. using the installation disc for system repair and so I was wondering what they actually do. When I look back, I clean install my OS every two or three years. And my old computer (i5, 4th gen) returns with start up times of 7 seconds. But this enormous list from sfc made me question its usefulness... it is usually short.
You wrote: "if errors are found, the system will try to restore the original files". Do you think that answered my question, if sfc will attempt replace any telemetry or anything of the kind. So to speak, my question was what does MS man by "error"

 

That is simply not true.....