The deputy governor of the Bank of England is the latest high-profile figure to question whether share prices are illogically high.
Sarah Breedon said she expected share prices to fall to reflect the many risks facing the global economy.
As companies grow, they may issue shares. Many of the largest companies in the UK have shares which are bought and sold on the London Stock Exchange.
Their collective performance is often quoted amid a blizzard of numbers that may feel confusing and irrelevant.
Booms or falls in the stock market make the news, but rarely does anyone mention the FTSE 100 during a coffee with friends.
