system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is Berkshire Hathaway and how did it get so big?

I just don’t understand how?
gpt
It's an investment company, a company that buys other companies (or at least parts of them). It got big by making very very smart investments over a long period of time. Unlike day-traders (buy and sell quickly), or private equity (buy most of a poor performing company and fix it then sell it), Berkshire-Hathaway tends to place very long (years or decades) bets on companies that are already sound but undervalued and they believe will grow long term.

If you do this correctly, over and over for decades, you end up with a giant pile of money.