The price of one share of stock, which is set by buyers and sellers in the market. Share price can be used to find a company's total market value, as represented by market capitalization. Prices of a stock will move throughout the day.
Investors generally buy a stock they feel is "undervalued", and sell a stock they feel is "overvalued". For instance, if the price of AAPL is $600 dollars, it means the cost to purchase one share of Apple is $600 dollars.