Processing Sounds with Effects
introduction
Effects are tools which can change sounds subtly or dramatically depending on how they are used. That usage can improve or degrade the quality of the sound, so experiment and always step back and listen to what is happening with the processed version in comparison with the unprocessed versions. Don't forget that you can also mix the two, even in variable amounts over time!
Below is a collection of text and video that will give you some idea of the possibilities (or abuses) that effects provide.
text
an introduction to various kinds of effects: https://www.avid.com/resource-center/audio-effects-guide
another introduction to various effects: https://blog.landr.com/audio-effects-plugins-guide/
some advice on using reverb (particularly for music, but might be applied generally): https://www.tunecore.com/blog/2019/04/7-reverb-mistakes-that-will-destroy-your-mix.html
the index of all effects, generators, analyzers, and tools in Audacity: https://manual.audacityteam.org/man/index_of_effects_generators_and_analyzers.html
video
a brief introduction to effects processing: https://www.youtube.com/watch?v=NJ2WzLg5rDc
a quick preview of many kinds of effects: https://www.youtube.com/watch?v=Pxr4HwAR8Xo
a fun video on changing your voice in Audacity: https://www.youtube.com/watch?v=qPhWyoC2KHQ