Google Trends is an online search tool that allows the user to see how often specific keywords, subjects and phrases have been queried over a specific period of time.
Google Trends works by analyzing a portion of Google searches to compute how many searches have been done for the terms entered, relative to the total number of searches done on Google over the same time. Although the data provided by Google Trends is updated daily, Google includes a disclaimer that the data Trends produces "may contain inaccuracies for a number of reasons, including data sampling issues and a variety of approximations that are used to compute results."