An example: 

If fund $ETF is intended to trade large cap tech stocks and owns 10 shares of $AMZN at $2500, 100 shares of $MSFT at $200 and 100 shares of $AAPL at $300, the NAV of the fund is $75,000 or ((2500*100)+(200*100)+(300*100))... assuming the fund has no liabilities.