other SEC regulations define and prescribe the conditions for use of certain non-GAAP financial information. Our measure of “Free cash flow” meets the definition of a non-GAAP financial measure. Free cash flow is used in addition to and in conjunction with results presented in accordance with GAAP and free cash flow should not be relied upon to the exclusion of GAAP financial measures. Free cash flow reflects an additional way of viewing our liquidity that, when viewed with our GAAP results, provides a more complete understanding of factors and trends affecting our cash flows. Management strongly encourages shareholders to review our financial statements and publicly-filed reports in their entirety and not to rely on any single financial measure. 

Free cash flow, which we reconcile to “Net cash provided by operating activities,” is cash flow from operations reduced by “Purchases of fixed assets, including internal-use software and website development.” We use free cash flow, and ratios based on it, to conduct and evaluate our business because, although it is similar to cash flow from operations, we believe it is a more conservative measure of cash flows since purchases of fixed assets are a necessary component of ongoing operations. In limited circumstances in which proceeds from sales of fixed assets exceed purchases, free cash flow would exceed cash flow from operations. However, since we do not anticipate being a net seller of fixed assets, we expect free cash flow to be less than operating cash flows. 

Free cash flow has limitations due to the fact that it does not represent the residual cash flow available for discretionary expenditures. For example, free cash flow does not incorporate payments made on capital lease obligations or cash payments for business acquisitions. Therefore, we believe it is important to view free cash flow as a complement to our entire consolidated statements of cash flows. 

In addition, we provide operating expenses with and without stock-based compensation. We provide this information to show the impact of stock-based compensation, which is non-cash and excluded from our internal operating plans and measurement of financial performance (although we consider the dilutive impact to our shareholders when awarding stock-based compensation and value such awards accordingly). In addition, unlike other centrally-incurred operating costs, stock-based compensation is not allocated to segment results and therefore excluding it from operating expense is consistent with our segment presentation in the footnotes to our consolidated financial statements. 

Operating expenses without stock-based compensation have limitations due to the fact that they do not include all expenses primarily related to our workforce. More specifically, if we did not pay out a portion of our compensation in the form of stock-based compensation, our cash salary expense included in the “Fulfillment,” “Technology and content,” “Marketing,” and “General and administrative” line items would be higher. We compensate for this limitation by providing supplemental information about outstanding stock-based awards in the footnotes to our financial