[dne]

ETF = investment fund traded on a stock exchange.

Index fund = investment fund (mutual fund or ETF) that tracks an index, i.e. passively managed.

[MagicWishMonkey]

So is something like VSGAX an ETF or is it an index fund?

[elbows]

If I understand correctly, ETF and index fund are orthogonal terms. An ETF is traded on the stock market -- in contrast to a mutual fund which you have to buy through other channels.

An index fund tracks an index rather than being actively managed.

I don't know about VSGAX specifically, but it could be both an ETF and an index fund.

[dne]

It's an index mutual fund[1] that is also available as an ETF[2].

1: https://personal.vanguard.com/us/funds/snapshot?FundId=5861&...

2: https://personal.vanguard.com/us/funds/snapshot?FundId=0938&...

[tonfa]

Index fund, it isn't trading in an exchange.