system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does "top shelf" alcohol taste so much smoother than the cheap alcohols?

I know they throw around terms like "triple filtered" and stuff, but what exactly does that do and why does it affect the flavor and sensation the way it does?
gpt
When spirits are distilled, the liquid comes out in 3 parts, heads first, then the heart, then the tails. The heads and tails contain lots of nasty things such as fusel oils. The best spirits / top shelf producers only take a small part of the heart which contains the cleanest spirit. This means less hangover/bad shit in your body. The quality of the raw ingredients and distillation equipment/methods also contribute significantly to the end products quality. 

Also, if a spirit is aged for a long time in wooden barrels, this process rounds off the harshness that may be found in unaged spirits. This also imparts some of the qualities of the wood such as vanilla flavours/woodiness. It can also however add hangover-causing congeners due to the chemical relationship between wood and alcohol.