unable to scan files

So I run a full system scan and it say there are 50 file that can’t be scanned. Explanation please?

https://blog.avast.com/2014/02/28/how-do-i-handle-files-that-avast-cant-scan/

Eddy’s link does a good job explaining the why, but if you have concerns about the files you can post a screenshot and we can advise what the files are