A stock mutual fund that invests in equity securities without regard to whether a company is characterized as small, medium or large.

The term "cap" is shorthand for capitalization. The investment community measures a company's size by its market capitalization, which is calculated by multiplying the number of a company's outstanding shares by its current stock price.

There is no universal consensus on the exact definitions of the various market caps, but the following parameters are a good approximation:

Giant or Mega Cap: Above $200 billion
Large Cap: From $10 billion to $200 billion
Mid Cap: From $2 billion to $10 billion
Small Cap: From $300 million to $2 billion
Micro Cap: Less than $300 million

These designations inform mutual fund investors about the investment focus of the fund in terms of company size. In the case of an all-cap fund, the portfolio manager has complete freedom to invest in companies of any size.

Because of the inclusive nature of its holdings, a total stock market index fund would have an all-cap portfolio.