Berkshire Hathaway is a US Based conglomerate controlled by billionaire investor Warren Buffet. Warren Buffet currently is the largest shareholder owning a little over 25% of the company, and the stake represents 99% of his net worth.
Berkshire Hathaway controls 59 subsidiary companies holding a diverse list of businesses diversified by business type, geography and industries, many of Berkshire's subsidiary companies are themselves a diversified mix of businesses.
Berkshire also owns large stakes in more than 40 companies listed on the US share market, and some international investments.
On top of the business holdings above, Berkshire is currently sitting on a cash pile of roughly $40 Billion.