If you and I both think that Apple is a great stock to buy, we can both decide to buy it. Of course, if one of us is a really big buyer, the act of buying it might move the price such that my price might be different from yours (depending on which of us gets there first). But regardless, the general investment opportunity of buying Apple stock is available to each of us, independent of what the other does. The stock market is a democratic institution open to anyone who has money and a brokerage account.