msclkid - Microsoft Click ID
A method used by Microsoft to track user clicks and conversions.
Part of Microsoft Advertising

How I saw this in Google Analytics:
A visitor had viewed my page on either running Zoom on Windows 10S or just Windows 10S.

In any case it is Microsoft's atttempt at competing with Google. This is coupled with the move to restrict users of Windows to make their searches using Bing.
I have seen more searches finding my pages due to the fact that Microsoft are making purchasers of new Windows equiped hardware use the default Edge browser and the default Bing Search.
What Microsoft say about Auto-Tagging:
How this relates to Google
I have an investment in Google, I used to have one in MS.