Price to Cash Flow (P/CF) is exactly the same as Price to Earnings (P/E) the only difference is you are dividing cash flow by price instead of earnings. Just as it is with any valuation metric, the lower the number, the better the valuation, or stated more plainly, the cheaper the company is.
P/CF is simply telling you what multiple of cash flow you are paying, or put a different way, what multiple of cash flow the company is trading at.