FZROX "Fidelity ZERO Total Market Index Fund" is a mutual fund.

When to use it?

When not to use it?

The stated objective of the fund is "The fund seeks to provide investment results that correspond to the total return of a broad range of U.S. stocks."

Let us explain that sentence:

Basically everyone @ Fidelity that buys FZROX puts all their money in a big pot (5.7 billion dollars on July 31, 2020) and then proceeds to buy every stock in the US, some 2,466 holdings as of 6/30/2020.

So basically every public company in the US is partially owned by this 5.7 billion dollars.

Nobody ever in the history of stock markets has ever had long-term success picking just the winners and no losers. So how about we buy all of them, and then as the winners start to be noticed, we put more money in them, and less money in the losers? Sounds like a great idea, and that is basically what the FZROX mutual fund does for us.

As of June 30, 2020 22.7% of the 5.7 billion is tied up in just 10 companies:

These 10 are currently the big "winners". Here winners has a very distinctive meaning. We mean the largest companies by "market cap". I.e. the companies worth the most money. It's a very easy way to select winners, which means we can keep costs very low. In fact this fund charges us $0.00 dollars per year to hold it! They make money buy loaning out the stocks they carry to people trying to game the stock market (usually to their demise). Which works out great for us!

If you go wanting to invest in other things, pay attention to the cost to hold it, ETF's and Mutual funds usually cost something, which is called an ER (an expense ratio) basically how much of a % they take out of the fund to pay themselves to make the fund available to us. Anything greater than 0.20% is probably a bad idea.

If you look on the https://fundresearch.fidelity.com/mutual-funds/summary/31635T708 you can see a lot more information about it.