VIOV is a creation of Vanguard. The market cap ETF is a collection of small-cap stocks in the US stock market.
VIOV: Vanguard S&P Small-Cap 600 Value ETF
VBR: Vanguard Small-Cap Value ETF
VBR is arguably the most popular small-cap ETF today. It was one of the first of its kind to be created, and it tracks the US small-cap value index.