system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are dogs' noses wet?
gpt
There are several reasons, actually.  The first, and most important, is that the chemo-receptors (the things that actually pick up smells) on a dog's nose are more functional when wet.  Similarly, our tongues can't taste anything when they are dry (stick your tongue out, let it dry, put something salty on it).  Same idea.  So the dog excretes a mucous that keeps the dogs nose wet, allowing the chemo-receptors to pick up smells.

Less importantly, dogs don't sweat, but they need to shed heat.  The nose is a piece of exposed (not furry) flesh that can be easily licked to take advantage of evaporative cooling.