As a new W10 user Audacity 2.4.2 I am reading the manual to get started! I see under Noise Reduction the following:
Noise Reduction
Audacity can remove some kinds of noise from a recording. Noise Reduction is an \xe2\x80\x98audio effect\xe2\x80\x99, one of the fiddlier audio effects to use. This effect works best with fairly constant noise like background hiss. You first select audio that is just the noise and create a \xe2\x80\x98noise profile\xe2\x80\x99. Once Audacity knows the noise profile, it can reduce the loudness of noise of that kind in audio you select.
Not sure if the “\xe2\x80\x98audio effect\xe2\x80\x99” etc. is a typo or if I am missing something. 
Brewster
Those numbers are supposed to be “quotes”, but something has gone wrong in the conversion to html. It should read:
Noise Reduction
Audacity can remove some kinds of noise from a recording. Noise Reduction is an ‘audio effect’, one of the fiddlier audio effects to use. This effect works best with fairly constant noise like background hiss. You first select audio that is just the noise and create a ‘noise profile’. Once Audacity knows the noise profile, it can reduce the loudness of noise of that kind in audio you select.
Thanks Steve. Figured something like that. This was really just an FYI.
Hopefully we’ve fixed all such occurrences for the next version of the manual.