system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: when people use a supercomputer to supercompute things, what exactly are they doing? Do they use special software or is just a faster version of common software?

Also, I don't know if people use it IRL. Only seen it in movies and books and the like.
gpt
They are mostly fast because of multiple processes at the same time. The do not work well on linear problems and scale best on tasks that can be done in parallel. They have special schedulers that assign calculations to cores and collate the results. 

Its more like a hundred or thousand PCs all working together on one problem.