Warren Buffett says invest in what you know

Billionaire Warren Buffett says investors should all stick to areas they know when they are deciding what companies to invest in. He calls that concept your "circle of competence."

Buffett says that over time he has expanded his circle a bit, but he has also found areas where he's incompetent and shouldn't be investing.

Buffett has famously avoided investing in most high-tech stocks over the years because he felt that he couldn't reliably predict which firms would dominate in the future. But in recent years, Buffett's Berkshire Hathaway has become a major shareholder in Apple.

He spoke Saturday at the conglomerate's annual shareholders meeting in Omaha.

Buffett's company reported a nearly $23 billion jump in its first quarter earnings because of a major swing in the paper value of its investments.

Berkshire Hathaway said it made $21.6 billion, or $13,209 per Class A share, in the first quarter.