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Almost nine gigabytes in size: Windows update 24H2 creates an undeletable cache file
(www.digitec.ch)
This is a most excellent place for technology news and articles.
It should fix system files that are not in expected state (I assume corruption, missing, wrong permissions etc.). Maybe it was more useful in the past, but after trying it couple times around 8 years ago and never seeing any benefit, I have never thought of using it since.
My colleague said it fixed some random issue once or twice after he was out of ideas.
If system is truly messed up, it's often faster and more reliable to just reinstall it, especially if you do not have much custom config.