system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is a “super computer” and what can it do?
gpt
Thus far no ELI5....

Humans did math with pen and paper or whatever until calculators were created. Which does basic math for us quickly. 

A computer is basically a calculator created to do MORE math faster. A regular calculator can do 1 "math" at a time.

A 5ghz CPU in a desktop computer can do ~5 billion of "Maths" per second.

So a super computer is basically a bunch of regular computers working together.

So if a super computer has the equivalent 1,000 of Desktop computers working together it 1,000*5billion = 5 trillion "Maths" per second.

Being able to do the same math as 5 trillion calculators in 1 second allow us to analyze incredibly large amounts of data faster. Data analysis is the core of prediction of things. Such as weather.

TLDR: A bunch of computers connected to each other can do Math faster than 1 computer alone.