Difference of NAV and market price on stock shares and funds

For the case of companies, my understanding is that the NAV (net asset value) is all its assets minus its liabilities. Then, this value is divided by the total number of shares the company has issued and that gives the NAV per share. On the other hand, the market price of a share is the price to which it trades, which we could say incorporates factors as confidence and expected potential gains. Therefore we can conclude that the market price is way more volatile than the actual NAV, due to these ‘psychological factors’. (please correct me if I’m wrong)

However, according to this investopedia article, a mutual fund’s NAV is directly its per-share market value. Then, the concept of NAV is very different in the case of stock shares and mutual fund shares, since the latter is not based in pure physical assets and liabilities, but already incorporates the volatility of market prices. Have I understood it correctly?