That is almost always the first Google Analytics interview question you will face. The Google Analytics is a free web analytics tool offered by Google to help you track and analyze the performance of your website.

The GoogleAnalytics records various activities of users when they visit your site like user engagement, visitor flow, number of conversions, along with attributes such as age, gender, interests with the help of tracking code.

The Google Analytics aggregates the data in multiple ways like User level, Session level, Pageview level, Event level.

That is the main purpose of the tool is to help you make decisions to improve the site performance and revenue.