Financial Terms - Net Asset Value

What does it means...
A mutual fund's price per share or exchange-traded fund's (ETF) per-share value. In both cases, the per-share dollar amount of the fund is derived by dividing the total value of all the securities in its portfolio, less any liabilities, by the number of fund shares outstanding.

In terms of corporate valuations, the value of assets less liabilities equals net asset value (NAV), or "book value".

What investopedia says...
In the context of mutual funds, NAV per share is computed once a day based on the closing market prices of the securities in the fund's portfolio. All mutual fund’s buy and sell orders are processed at the NAV of the trade date. However, investors must wait until the following day to get the trade price.

Mutual funds pay out virtually all of their income and capital gains. As a result, changes in NAV are not the best gauge of mutual fund performance, which is best measured by annual total return.

Because ETFs and closed-end funds trade like stocks, their shares trade at market value, which can be a dollar value above (trading at a premium) or below (trading at a discount) NAV.

Details here.
NAV explained