Web analytics is the measurement, collection, analysis and reporting of Internet data for understanding and optimizing Web usage.
 Web analytics is not just a tool to measure website traffic, but can be used as a tool for business research and market research. It helps to estimate the traffic to the website after any modifications or new change. Web analytics provides information on the number of visitors, page views, etc. to measure the popularity and traffic trends to help you do market research.

For more information 'Web Analytics' and 'Google Analytics'.