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&...
27 karma · joined September 24, 2011
1: https://personal.vanguard.com/us/funds/snapshot?FundId=5861&...
2: https://personal.vanguard.com/us/funds/snapshot?FundId=0938&...
Index fund = investment fund (mutual fund or ETF) that tracks an index, i.e. passively managed.
E.g. in Intel's product spec for the DC S3500 series, the data retention parameter is specified as: "3 months power-off retention once SSD reaches rated write endurance at 40 °C".