Google Analytics is a free tool that allows companies to track and analyze website traffic. It provides detailed reports on metrics like visitors, pageviews, goals, and e-commerce transactions. To use it, one needs to install the Google Analytics tracking code on every page of their site. Profiles and filters can then be used to segment traffic and filter out unwanted data. Additional features like goals, funnels, and e-commerce tracking provide further insights. Regular expressions are often used with filters to match patterns in tracked data.