Brk
In short
BRK is the stock ticker symbol for Berkshire Hathaway Inc., a massive American holding company led by Warren Buffett.
In plain words
It is a giant company that owns many smaller businesses like GEICO and Duracell. People buy shares of BRK to invest in a wide variety of industries all at once.
A simple example
If you buy one share of BRK, you are effectively putting a small amount of money into insurance, railways, and energy companies simultaneously.
Why it matters
It is one of the most famous investment vehicles in the world. Its performance is often used as a benchmark for how well value investing is working.
Easy to mix up
Do not confuse it with BRK.B, which is the class B share that is easier for small investors to buy.