What are fuses used for?


I have, I’m sure to many, a very dumb question. I keep reading about fuses.  I have a fairly sophisticated system and have never come across the need for a fuse.
Can someone tell me where these fuses go and what they’re used for?
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Fuses can be used to change or control the sound just like speaker cables, interconnects, capacitors, power cords or any wire or cable. Capacitors serve a function just like fuses. Yet capacitors are also directional due to the wire running through them. Since all wire is directional, including the teeny tiny fuse element, all cables, capacitors, fuses sound better in one direction vs the other direction. In one direction, that usually cannot be predicted by the user, the sound will be relatively more coherent, more natural and more musical than the other direction.

This proposition regarding directional can be illustrated most easily by reversing the direction of interconnects and evaluating which direction sounds better. Voila! I’m not referring to shielded interconnects, since they have their own independent issue regarding direction.
I almost forgot. Fuses are also used to torture naysayers. That’s the most fun feature of fuses as we have seen.  Fun for everyone! 
“Contrary to popular misconception by the ill-informed fuses (like all wire) have NO effect upon sound quality. To think otherwise is to believe in magic!”

Here we go again.....hope this thread doesn’t turn into heated debate on the effectiveness of aftermarket vs. stock fuses. 
If you have the manuals for your equipment it shows you where to replace a fuse. If you don't have the manuals you can probably download them from the manufacturer.