This option allows the quick removal of all user-installed trusted credentials from the device.
What the list of trusted credentials is for
Devices and browsers contain a pre-installed list of trusted certificate authorities, indicating which companies the device trusts to provide secure certificates for websites or other purposes.
In addition to the pre-installed trusted credentials, in some cases it is possible for you to add your own trusted authorities to your device, which will appear as user-installed trusted credentials. For example, your company might use its own secure certificates for its corporate network, and require you to install its trusted credentials on your device. These credentials may have been installed by software provided by your company.
This setting removes all user-installed trusted credentials from the device, but does not modify or remove any of the pre-installed credentials that came with the device.
You should not normally have reason to do this. Most users will not have any user-installed trusted credentials on their device.