Adjusted OIBDA . We define Adjusted OIBDA as operating income before depreciation and amortization excluding the impact of restructuring costs, non-cash equity-based compensation, gains and losses on all disposals of assets, noncash asset impairments and write-offs and special items. We consider Adjusted OIBDA to be a useful metric for management and investors to evaluate and compare the ongoing operating performance of our business on a consistent basis across reporting periods, as it eliminates the effect of noncash items such as depreciation of tangible assets, amortization of intangible assets that were primarily recognized in business combinations, asset impairments and write-offs, as well as the effect of restructurings, gains and losses on asset sales and special items, which we do not believe are indicative of our core operating performance. We exclude the impacts of equity-based compensation to allow us to be more closely aligned with the industry and analyst community. A limitation of this measure, however, is that it does not reflect the periodic costs of certain capitalized tangible and intangible assets used in generating revenues in our business or the current or future expected cash expenditures for restructuring costs. The Adjusted OIBDA measure also does not include equity-based compensation, which is and will remain a key element of our overall long-term compensation package. Moreover, the Adjusted OIBDA measures do not reflect gains and losses on asset sales, impairment charges and write-offs related to goodwill, intangible assets and fixed assets or special items which impact our operating performance. We evaluate the investments in such tangible and intangible assets through other financial measures, such as capital expenditure budgets, investment spending levels and return on capital.
Free Cash Flow. We define Free Cash Flow as cash provided by operating activities, less capital expenditures, product development costs and principal payments on capital leases. We consider Free Cash Flow to be a liquidity measure that provides useful information to management and investors about the amount of cash generated by the business that, after capital expenditures, capitalized product development costs and principal payments on capital leases, can be used for strategic opportunities, including investing in our business, making strategic acquisitions, and strengthening the balance sheet. Analysis of Free Cash Flow also facilitates management's comparisons of our operating results to competitors' operating results. A limitation on the use of this metric is that Free Cash Flow does not represent the total increase or decrease in cash for the period because it excludes certain non-operating cash flows.
Unique Visitor Metrics
We utilize unique visitor numbers to evaluate the performance of AOL Properties. In addition, we utilize unique visitor numbers to evaluate the reach of the AOL Advertising Network, which includes both AOL Properties and the Third Party Network. Unique visitor numbers provide an indication of our consumer reach. Although our consumer reach does not correlate directly to advertising revenue, we believe that our ability to broadly reach diverse demographic and geographic audiences is attractive to brand advertisers seeking to promote their brands to a variety of consumers without having to partner with multiple content providers. The source for our unique visitor information is a third party (comScore Media Metrix, or “Media Metrix”).