Cash makes the world go round. You need cash to make cash, as unfortunately no-one has yet found a tree from which we can go and pluck 20 notes at will. Companies raise cash in various different ways, either though bank loans, a myriad of novel debt offerings, venture capital funds, or through a public offering of shares. Think of how you would go about opening the corner store that you've so longed for over the years. Large companies think in exactly the same way, although on a much bigger scale.
Companies live and die on the amount of cash they generate.
For all the money they spend on acquiring new pieces of machinery or computers or spend on staff wages, if they don't receive a decent return on that investment, they will die. A company that generates above average amounts of cash will succeed in building shareholder value. That additional cash can be reinvested back into the business, can be spent on earnings enhancing acquisitions, can be paid out to shareholders as dividends or can be used for a share buyback scheme. Without any cash, a company treasurer will get to know her bank manager pretty well, but perhaps not on the friendliest of terms. Cash earnings are much different from accounting earnings.