What is Clickstream?

Legal Definition
A clickstream is the recording of the parts of the screen a computer user clicks on while web browsing or using another software application. As the user clicks anywhere in the webpage or application, the action is logged on a client or inside the web server, as well as possibly the web browser, router, proxy server or ad server. Clickstream analysis is useful for web activity analysis, software testing, market research, and for analyzing employee productivity.
-- Wikipedia
Legal Definition
Mouse clicks or keystrokes a user makes in sequence or as a 'flow' while navigating through webpages or websites. Web advertisers custom-tailor their advertisements to this specific customer, by determining the user's interests and preferences by the clickstream record.